What is an API?
Answer out loud or in your head first, then compare.
Answer
An API is an agreed way of using the capabilities of another program or library. It defines which operations you can call, what data to pass and what response to expect. In web apps we often mean an API exposed by a server, but the concept is broader.
For example, the frontend sends a request to create a project instead of connecting to the database itself. The server checks the data and permissions and then returns the result. A well-documented API should also explain errors and limits. The fact that a client can send a request doesn't mean it has the right to perform every operation.
Why it matters: Lets you talk precisely about the boundaries of an application.
Possible follow-ups: What should the contract between frontend and backend include?
How did it go? Be honest — “Not yet” puts the question on your review list.
Further reading
- AWS: What is RESTful API?(opens in a new tab)Accessed 22.10.2026. Resources, operations and REST principles.