It's a distributed ledger, that you can deploy a computer program to. Use cases extend outward from there.
Like self custody: the idea of owning a valuable and transferable asset by only holding a private key was not possible prior to Bitcoin. The closest comparison might be a domain name: people feel like they own those, but they are just renting them from a registrar who leases you the account and ability to edit your domain records.
This applies all over Ethereum, DeFi, ENS, NFTs. Look at Aave, that allows lending and borrowing without a custodial service provider.