Uh, can someone (kindly) explain Bitcoin to this money dummy?
You can think of fiat money as an accounting ledger. The ledger keeps track of who owns what money on the system. The ledger in our banking system is centralized in that a controlling entity maintains the ledger. Your bank has a ledger for its customers and the Fed has one for its member banks.
Bitcoin is a decentralized ledger. There is no centralized authority maintaining the ledger which is distributed among hundreds of thousands of computers around the world. The value recorded in the ledger is denominated in Bitcoin which is programmatically limited to 21 million units.
That’s the very broad outline. I can get into a bunch of technical details and practical implications if you want. It’s easier to do that via questions and answers.