If we consider blockchain to be a ledger or a book, a block can be compared to a page or a table in which we record a collection of confirmed transactions. Each block stored in the blockchain is uniquely identified by a hash, and composed of a header and a body.

The header encloses information about its creation (timestamp, Merkle root, Nonce, difficulty target, and version), and a reference to a previous block, whereas the body is a collection of the accepted transactions. 

When a block is successfully validated (mined), it becomes part of the official blockchain. New bitcoins are generated in the block (a coinbase transaction) and paid to the validators (or miners).