Blocks
A block in the Bitcoin blockchain is like a page in a ledger or a record book. It contains a list of transactions that have been verified and added to the blockchain.
Apart from transaction data, each block also contains a block header which consits of:
- version: version number
- hash of previous block: hash of the previous block header
- merkle root: merkle root of the transactions included in the block
- timestamp: epoch timestamp of the block
- bits: network target difficulty
- nonce: random value generated during the process of mining which must match certain criteria
At the time of writting Bitcoin had 807752 blocks. You can see the number increase by querying your Bitcoin node or use public Bitcoin explorer.