Use this reference alongside a real question: what does the field mean, what does the tool know, and what should stay private? Definitions describe concepts, not current fees, prices, or software-version requirements.
A
- API
- An application programming interface: a defined way for software to request or exchange information. Explorer APIs can expose read-only blockchain data. A node’s administrative RPC interface is a different security boundary and should not be made public simply because both are called APIs.
- Address
- A representation used to specify a receiving destination for common Bitcoin output types. It is not a complete wallet or a verified personal identity. A wallet may generate multiple receiving and change addresses, so an explorer’s view of one address can be narrower than the wallet’s own records.
B
- BTC
- The commonly used unit for bitcoin amounts. One BTC equals 100,000,000 satoshis. Always check whether a wallet, explorer, or API is displaying BTC, satoshis, or another unit before comparing values or calculating a fee.
- Block
- A group of transaction data linked to the preceding block through its header. A confirmed transaction belongs to a particular block on the chain view being followed. A block explorer makes those records readable, while a full node independently checks them against its rules.
- Block explorer
- An indexed, readable view of public blockchain information. It can present blocks, transactions, and address activity. The provider’s source, data freshness, and labeling choices matter. A public explorer is useful for inspection but is not a wallet, a recovery service, or a substitute for independent validation.
- Block hash
- An identifier derived from a block’s header. Use it to refer to a particular block rather than relying only on height. Competing blocks can share a height, so a hash is important when preserving a precise transaction or confirmation observation.
- Block header
- The part of a block that commits to key information, including its predecessor and transaction commitment. It is central to linking blocks and proof of work. A beginner generally does not need to decode every header field to navigate an explorer responsibly.
- Block height
- A block’s position in the chain, counted from the genesis block at height zero. Height gives useful context but does not uniquely identify a block across competing chains. Preserve the hash as well when a precise reference is needed.
- Broadcast
- The act of sending a transaction into a network connection for propagation. A wallet reporting a broadcast attempt is not the same as a transaction being included in a block. A missing explorer result should be investigated with the sending record and correct network.
C
- Change
- A new output that can return the unused remainder of spent inputs to the sender’s wallet. A transaction spends an earlier output as a whole rather than leaving a partial amount inside it. External explorers do not necessarily know which output is change.
- Coin selection
- The wallet process of choosing which available outputs to use as transaction inputs. The resulting structure can affect fees and public links between outputs. A wallet’s total balance does not, by itself, tell you which pieces a particular payment will spend.
- Coinbase transaction
- The special first transaction in a block, used to claim the permitted block subsidy and transaction fees. It is not an ordinary payment spending previously created outputs in the same way. The term describes a protocol transaction and is not a reference to a particular exchange.
- Confirmation
- Inclusion of a transaction in a block on the chain being followed. Additional blocks built on top increase confirmation depth. A count is contextual and can change with the chain view. It is separate from a business’s internal account-crediting decision.
- Custody
- The arrangement governing control over spending authority. In a custodial account, a provider manages keys on a customer’s behalf. A self-custodial wallet places different recovery and security responsibilities on the user. Establish the actual model rather than relying on an app’s label.
D
- Descriptor
- A structured description used by supporting wallet software to specify output-related information and how to derive it. A descriptor may reveal extensive viewing information or contain private material depending on its contents. Treat exports according to what they actually include, not merely their filename.
- Double spend
- An attempt to spend the same earlier output more than once in conflicting transactions. Bitcoin’s validation and chain-selection mechanisms address conflicts in the accepted history. A visible unconfirmed transaction should not be treated as equivalent to settled inclusion simply because a website displays it.
F
- Fee
- For an ordinary transaction, the difference between the total input amount and the total output amount. It is not normally a separate output addressed to a recipient. Distinguish this total amount from the fee rate used to relate cost to transaction size.
- Fee rate
- A transaction’s fee relative to its size, often expressed as satoshis per virtual byte. Two transactions can pay the same total fee but have different rates. An estimated rate for a confirmation target is not a guarantee of an exact confirmation time.
- Full node
- Software that independently validates blocks and transactions against its consensus rules. Running a full node is different from mining. A wallet benefits from a chosen node connection only when it is actually configured to use that infrastructure.
G
- Genesis block
- The first block of the Bitcoin chain, at height zero. It provides the starting point for block-height references. You do not need a live dashboard or a current block count to understand its role in the chain’s structure.
I
- Indexer
- Software that organizes blockchain data to answer particular queries efficiently. An explorer can use an indexer for address-history searches. Indexing and validation have different purposes; an indexer may depend on a node without replacing that node’s consensus checks.
- Input
- A part of an ordinary transaction that references an earlier output being spent. The reference includes the earlier transaction ID and output index. Inputs are records of spending relationships, not automatic proof of the personal identity of a sender.
M
- Mainnet
- The production Bitcoin network, as distinct from testing environments. Always keep network identity explicit in a lookup, application configuration, and exported record. A transaction ID on the wrong network can produce an unavailable result without explaining the mistake.
- Mempool
- A node’s local collection of accepted transactions not yet included in its accepted blockchain. It is not one universal queue shared identically by every participant. A public provider’s mempool display is an observation from that infrastructure, not a guaranteed ordering for future blocks.
- Mining
- The process involved in constructing candidate blocks and performing proof of work. It is distinct from running a validating node or displaying an explorer. A node installation does not automatically create mining activity or a promised financial return.
O
- Output
- A transaction component containing an amount and spending conditions. New outputs can later be referenced by transaction inputs. A payment may create several outputs, so a transaction’s total output value should not automatically be treated as the amount paid to one recipient.
- Output index
- The zero-based position of an output within a transaction, often called vout. Combined with the transaction ID, it identifies the specific output. Index one refers to the second output, a detail worth preserving in technical notes and API integrations.
P
- Private key
- Secret information used as part of authorizing the spending of relevant outputs. It is not needed to read a public transaction in an explorer. Never provide private keys to a lookup site or an unsolicited support contact claiming to unlock a payment.
- Proof of work
- The mechanism requiring a qualifying block-header hash to satisfy the network’s difficulty condition. Nodes validate the proof along with other rules. It is part of how competing valid histories are evaluated, not a claim that a website’s data has been independently checked by its visitor.
- Pruning
- A node mode that removes older block files after validation according to its retained-data target. It reduces stored historical data without meaning that those blocks were skipped during initial validation. Other services may require historical access or indexes incompatible with a particular pruning plan.
R
- RPC
- Remote procedure call: an interface for requesting operations from software such as a Bitcoin node. Depending on configuration and methods, it can expose privileged capabilities. Do not confuse it with an unrestricted public read-only explorer endpoint or put administrative credentials in browser code.
- Recovery phrase
- A secret backup representation used by supporting wallets to help recover key material. Exact recovery requirements depend on the wallet and setup. A public block explorer has no legitimate need for a recovery phrase, and a screenshot or support message is not an appropriate place to share it.
- Reorganization
- A change in which blocks belong to the chain a node follows when competing valid history is resolved. Confirmation observations can change as a result. Preserve block references and observation times rather than treating a first displayed status as permanently fixed.
S
- Satoshi
- One hundred-millionth of a bitcoin. Many explorer APIs represent transaction amounts as integer satoshis. Confirm the documented unit of each interface and preserve exact amounts through calculations instead of casually mixing floating-point values and display formats.
T
- Transaction ID
- An identifier for a Bitcoin transaction, commonly abbreviated TXID. Use the complete value from the sending wallet or service when checking a payment. A platform’s internal withdrawal reference is not necessarily a Bitcoin transaction ID.
U
- UTXO
- An unspent transaction output: a previously created output that remains available to be spent when its conditions are satisfied. A wallet’s balance can summarize many such outputs across addresses. Understanding UTXOs helps explain change, coin selection, and why one address is not a complete wallet.
V
- Virtual byte
- A unit derived from transaction weight and used in common fee-rate calculations. It accounts for the weighting of witness data rather than simply equaling every transaction’s raw byte count. Keep satoshis per virtual byte distinct from other fee-rate units.
W
- Wallet
- Software or a broader setup for managing receiving information and a payment workflow. Some components hold signing authority; others are watch-only. Determine the actual control, recovery, and network-connection model rather than assuming every application called a wallet behaves alike.
- Watch-only
- A viewing arrangement that can monitor relevant activity without the private keys required to sign. The information it uses may still expose broad wallet history. Lack of spending authority does not make a wallet-wide export harmless to share.
Technical referenceThese definitions are starting points. Consult the Bitcoin developer reference for formal structures and project documentation for current implementation behavior.