When is a key an API key
Somewhere in your password manager sits a long string that starts with sk. That is a . It proves to a that requests come from your account, and whoever holds it can spend as you. A password opens your door. A key signs your name.
It becomes an API key the moment a program uses it instead of you. Paste it into a tool and you have handed that tool your signature, at whatever the key allows. Good tools ask for the narrowest scope that still works. Bad tools ask for everything and call it convenient.