Yeah, it's a bit overloaded. There are keychains (.keychain files) and keychain items (secrets inside of them). The keychains are visible in the Keychain Access app, but also available in the 'security' command line. And then there are modern keychains, those are more like SQLite databases and those can have anything from SQLCrypt type of management to Secure Enclave DEKs.

Security is pretty difficult to get right, so many tradeoffs as well.