A blockchain block is a protocol-defined record that can group transactions with other data used by that network. It is one piece of the chain of records that gives a blockchain its name.
What a block contains
There is no single block format for every blockchain. The rules come from the protocol. Bitcoin documentation describes a block as containing transactions and a header. Ethereum describes blocks as batches of transactions with their own defined fields.
A block can therefore contain more than a simple list of transfers. Depending on the network, it may also include data that helps participants verify where the block fits in the chain and whether it follows that network’s rules.
Why blocks form a chain
In Bitcoin, a block header includes the hash of the preceding block header. Ethereum documentation likewise describes blocks as including a hash of the preceding block. These references connect records in sequence.
That does not mean every blockchain uses identical fields, timing or validation arrangements. Bitcoin’s block structure and Ethereum’s block structure are different examples of protocol-specific designs.
What a block does not tell you on its own
A block is a record within a technical system. Its existence does not, by itself, prove the identity of a person connected with a transaction, the meaning of an outside event, ownership of an off-chain item or the value of anything mentioned in it.
Sources
- Bitcoin Developer Documentation: Block
- Bitcoin Developer Documentation: Block Chain
- Ethereum.org: Blocks
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