A blockchain is a digital ledger that records a series of transactions or events in a secure, transparent, and decentralized way. It is called a “chain” because each block of data is linked to the previous one, forming a chain of blocks. Each block contains a list of transactions that have been verified and added to the blockchain.

The data in a blockchain is stored in a distributed network of computers, rather than in a central location, making it more secure and resistant to tampering. Each computer in the network, known as a node, has a copy of the entire blockchain and verifies transactions to ensure their validity.

In order to add a new block to the chain, a network of nodes must come to a consensus that the new block is valid. This consensus is reached through a process called mining, where nodes compete to solve a complex mathematical puzzle. The first node to solve the puzzle earns the right to add the new block to the chain and is rewarded with cryptocurrency as an incentive for contributing to the network’s security.

Once a block is added to the chain, it cannot be altered or deleted without also changing all subsequent blocks in the chain, which would require a majority of the network’s computing power. This immutability and transparency make blockchains useful for a variety of applications, such as cryptocurrency transactions, supply chain tracking, voting systems, and more.