API

API stands for application programming interface. It is the doorway a service exposes so other software can read its data or tell it to do something, in a structured and predictable way. When one tool 'connects to' another, it is almost always talking to its API.

APIs are what make automation possible. If a tool has one, its work can be wired into a workflow instead of done by hand. It is why the honest test for connecting a system is usually 'does it have an API?'