In cryptocurrency, a block is a record in a digital ledger called a blockchain that contains a list of transactions. These transactions are verified by network participants through a process known as mining. Once a group of transactions is verified and added to a block, it is then added to the blockchain in a sequential order.

Each block typically includes a reference to the previous block, creating a chain of blocks hence the name blockchain. This linking of blocks ensures the immutability and security of the information stored in the blockchain.

Blocks also contain a hash value, which is a unique identifier generated by complex mathematical algorithms. This hash value is used to connect each block to the rest of the blockchain, making it easy to verify the integrity of the data.

Overall, blocks play a crucial role in maintaining the integrity and transparency of transactions in a decentralized and secure manner within the cryptocurrency network.