You can think of the API like a messenger that runs back and forth between your database and other services to collect information and eventually pass it to your front-end. Each individual command that the messenger (API) knows is called an API Endpoint.
You've probably heard of the term REST API or RESTful API. REST is simply an architectural style that the vast majority of web services use to communicate with one another. It stands for representational state transfer and was created by the computer scientist Roy Fielding.