API
An application programming interface — the contract that lets one piece of software talk to another, like posting to a platform in code.
An API (application programming interface) is the defined set of endpoints and rules that lets one program drive another. On social platforms, the API is how tools read and write on your behalf — fetching metrics, pulling comments, and posting content programmatically rather than by hand in the app.
It's the foundation under any social media scheduling tool: the scheduler holds your queue, then calls each platform's API at the right moment to publish. Where an API is request-and-response, a webhook flips the direction so the platform calls you.
See also