Can you explain what Android Interface Definition Language (AIDL) is and what it is used for?

Android Interface Definition Language (AIDL) is a tool in Android that allows defining an interface for inter-process communication (IPC).

When an application consists of multiple processes, AIDL helps describe methods that can be called remotely from another process. This is necessary because processes in Android are isolated, and direct method calls are impossible.

AIDL generates code that facilitates data transfer between processes by serializing and deserializing parameters and call results.

Example of using AIDL:

1. Create a .aidl file with the interface description.
2. The compiler generates the interface and helper classes.
3. Implement this interface in the service.
4. The client connects to the service and calls methods through the generated interface.

Thus, AIDL is used to implement remote method calls between processes in Android.