Blockchain is a decentralized and secure digital ledger that is used to record transactions across a network of computers. It operates through a distributed database, which means that data is stored on multiple computers rather than on a single central server.

In a blockchain, transactions are grouped into blocks, which are then added to the chain in a linear, chronological order. Each block contains a unique code called a "hash" that links it to the previous block in the chain. This creates an unalterable, tamper-proof record of all transactions, ensuring the integrity and transparency of the data.

The decentralized nature of blockchain makes it resistant to tampering or interference from a single entity, as there is no central point of control. Instead, the network of computers that make up the blockchain work together to validate transactions and maintain the ledger, making it highly secure and tamper-proof.

Blockchain technology has many potential applications, including the secure transfer of digital assets, the management of digital identities, and the creation of decentralized applications. One of the most well-known uses of blockchain technology is in cryptocurrencies, where it is used as the underlying infrastructure to support secure, decentralized transactions.