A validated batch of transactions linked to the block before it.
Block meaning
A block is a protocol data structure containing a header and an ordered set of transactions. It gives Bitcoin a shared sequence of history. A valid block must satisfy consensus rules, including proof of work and limits on what its transactions may spend.
How it works in Bitcoin
The header commits to the previous block header and to the block's transactions through a Merkle root. Changing an old transaction changes that commitment, which changes the header hash and breaks the proof-of-work chain built after it.
A simple example
If a payment appears in block 900,000, the next valid block built on it gives that payment one additional layer of confirmation depth. Wallets often describe the containing block as the first confirmation.
Why Block matters
Network terms explain how independently operated software shares, validates and orders information. They help separate a convenient data viewer from the rules a node actually enforces.
What people often get wrong
A transaction being broadcast does not mean it is in a block. Until a miner includes it and nodes accept that block, the transaction remains unconfirmed and may be replaced or dropped under some conditions.
Quick checks before using the term
- Which actor performs this job?
- Is the behavior a consensus rule or an implementation choice?
- What evidence can a node verify independently?
Apply these questions to the concrete example above. A precise answer is more useful than repeating the definition without naming the actor, rule or failure path.
Check the primary reference
This entry is written in plain English, but the technical source is available when you need exact protocol detail.
Bitcoin Developer Guide: Block Chain ↗