What Is a Blockchain and How Does It Secure Transactions?

A blockchain is a decentralized, immutable digital ledger that records transactions in a series of connected blocks. Each block contains a cryptographic hash of the previous one, linking them together in a secure chain.

This structure ensures that once a transaction is recorded, it cannot be altered. Security is further enhanced by decentralization, where the ledger is distributed across numerous computers, requiring consensus to validate any new entries, thus preventing fraud and unauthorized changes.