An API proxy is a middle service that receives a request from an app, passes it to another service, and returns the response. The app talks to the proxy, which talks to the service on its behalf.
Imagine a receptionist who takes a visitor's request to the right office and brings back the answer. A proxy can help manage where requests go and how they are handled.
A proxy does not automatically make an app secure. It needs careful setup, especially if requests contain private information or secret access keys.