Blockchain is the tech behind bitcoin. It’s sometimes called a distributed ledger, which is a way of saying that everybody in the blockchain network has a ledger on their computer, and when a transaction occurs, every copy gets updated. If everyone can see the transaction, then effectively we have interoperability without having interoperability. If I have to interoperate with someone, I have to trust them with a hole through my firewall. With blockchain, all I need to trust is the blockchain.