For a full list of calls available, see the API Reference page.
The session based authentication uses a session key instead of a token. It is mostly used with the Unity3d and Flash interfaces.
The id.net Game API provides application level features like achievements on top of the session based auth. It is based on the open source Playtomic API but is not directly compatible.
The id.net Analytics API gives application developers insights into how their game is being distributed and used by end users.
There are a limited set of server to server push notifications available. When a user has made a change, updates are sent by id.net to a receiving backend system.