What is the "APM, Web Application" module used for?

BIG-IP Access Policy Manager (APM) secures and differentiates access to your applications, data, network, and the cloud based on user identity and context. That means it gives you centralized control over who’s able to access your network or cloud, which applications they can access, and the devices and locations from which they can access those apps.

In short, BIG-IP APM unifies and enforces identity-based, context-aware, dynamic policy-driven application access control—regardless of the location of the user or the application

Eg: SSL VPN

APM-Webapplication article link is mentioned below

https://support.f5.com/csp/article/K13425