The blockchain can be either stored as a flat file or as a database.

A blockchain is a decentralized and distributed ledger technology that stores data across a network of computers. The data in a blockchain is stored in blocks, and each block contains a list of transactions or other information. These blocks are linked together in a chronological chain, forming the blockchain. The entire blockchain is stored on each node (computer) participating in the network.

In summary, a blockchain is stored across a network of computers, with each node maintaining a copy of the entire blockchain. This decentralized and distributed nature enhances the security and immutability of the data stored on the blockchain.