A blockchain is a decentralized, digital ledger that records transactions on multiple computers. It is a type of distributed ledger technology (DLT) that allows multiple parties to reach consensus on the state of a database without the need for a central authority.
At a high level, a blockchain consists of a chain of blocks, each of which contains a record of multiple transactions. These transactions can be financial transactions, such as the transfer of cryptocurrency from one person to another, or they can be any other type of data that needs to be recorded and verified.
Each block in the chain contains a unique code, called a "hash," that identifies it and links it to the previous block in the chain. This creates a secure, chronological record of all the transactions that have taken place on the blockchain.
In order for a new block to be added to the blockchain, it must be verified by a network of computers, called "nodes." These nodes use complex algorithms to reach consensus on the validity of the transactions contained in the new block and to ensure that the block is added to the correct location in the chain.
Because a blockchain is decentralized and transparent, it is considered to be a secure and reliable way to store and verify data. It is used in a variety of applications, including cryptocurrency, supply chain management, and voting systems.