Pretty much, yes. The way an API *should* work (should being the "preferred" way) is with a RESTful API. Basically, you POST/GET/PUT/DELETE to a certain URL, and then action is taken on it based on the type of request (POST/GET/PUT/DELETE).
For example, if I had an API that showed my ToDos:
GET to /api/todos -> returns all todos
GET to /api/todos/<todo:id> -> returns one todo
POST to /api/todos -> inserts a new todo (parameters might be name, description, due by, etc)
PUT to /api/todos/<todo:id> -> update an existing todo
DELETE to /api/todos/<todo:id> -> delete an existing todo.
All of these might be stored in a database, or in a text file, or w/e. With an API it doesn't matter what happens in the background.. the API is technically all about how it's interfaced with.