Block Header

The header of any block, which usually contain at least the following (might differ per implementation):

• $n$: The current block number.
• $p$: the hash of the header of the parent block.
• $s$: the Merkel Tree root of the state of the blockchain, after this block has been executed
• $t$: the Merkel Tree root of all of the transactions that are in this block

How $p,s$ and $t$ are used to ensure interesting properties in blockchains are discussed in Blockchain Networks and Blocks, Transactions, And Blockchain Systems.