Blockchains are a form of Distributed Ledger Technology (DLT) that was originally developed as an accounting method for the cryptocurrency Bitcoin. It is a way of storing data without a centralized administrator, location or data storage. Nowadays blockchain technology is used for many other commercial applications other than verifying digital transactions.
It is possible to digitize, code and insert basically any document into the blockchain. This creates a record that can not be deleted or changed and the authenticity can be verified by anyone with access to the blockchain.