Coins, inventory, cars, loans, art, crypto kitties, sensor logs, records.. anything you'd put in a database, you could instead put into the distributed ledger and forget about it (at a price, the amount of data has to be very small but you can also buy hosting separately). Others can then have assurances about the integrity of that ledger without having to trust you either
The cherry on top is being able to write transform functions (ie programs) that all of the nodes simultaneously run so the ledger state can intelligently change based on conditions
What specific advantage does the blockchain provide here, given decentralisation is less efficient than the centralised cloud solutions already available from providers like AWS?
In what situations am I going to want to create a database in which not even I under any circumstances can delete things or change access rights?