Lots of people thinks that Blockchain is a database, actually its not. Blockchain is a digital ledger where any transaction can be processed related to Finance, Medical, and any field which include value
Actually, a blockchain is a
data structure.
It is, in bitcoins case, a public ledger. But it doesn't have to be (1) public, neither does it have to be a (2) ledger.
The basic idea behind the blockchain is to create an immutable structure of 'blocks' refering to the previous one, creating a 'chain'.
What kind of data is going to be stored inside of a blockchain, is completely up to the application utilizing this technology.