As the name indicate that Blockchain is chain of block that contain information.
It is type of distributed database. In Blockchain each digital document or information is timestamped which will ensure that document or information can’t be back dated or tempered. Blockchain is a distributed ledger or open distributed ledger which is completely open to everyone access. When data is recorded in Blockchain block it is very difficult to change it. As each block in Blockchain is consist of data, hash of previous block and hash of the current block.
Data store in Blockchain depend on the type of Blockchain. Once a block is creating it hash is calculate so changes in the data or block will also cause change in the hash value due to this reason Hash is also used for detection in the block. First block in any Blockchain is called Genesis block.