Blockchain is a decentralized ledger that records transactions across multiple computers in a secure and transparent manner. Each transaction is grouped into a block, and these blocks are linked together in chronological order, forming a chain. This structure helps ensure that once data is recorded, it cannot be altered without the consensus of the network.

The security of blockchain comes from cryptographic techniques that protect the information and verify transactions. Each block contains a unique hash of the previous block, creating a chain that is extremely difficult to tamper with. If someone tries to change a block, it would invalidate all subsequent blocks, raising suspicion among users.

Blockchain operates on a peer-to-peer network where all participants have access to the entire ledger. This transparency fosters trust among users, as anyone can verify the validity of transactions. Additionally, the lack of a central authority minimizes the risk of fraud and enhances efficiency compared to traditional systems. Overall, blockchain technology underpins many digital currencies, enabling secure, fast, and cost-effective transactions.