Blockchain a public ledger or a distributed database of all bitcoin transactions. It is an open-source technology, information is immutable and anyone can access the details at any time. As Blockchain is a distributed ledger, there will be no control or central authority of records stored.
Anyone in the network can add the data and cannot be deleted or altered further. Usually, the blockchain stores the data in terms of blocks, and those blocks are linked together like a chain and will be encrypted for security. To validate the transaction here Blockchain uses Proof of Work Mechanism.