Filter profiles can be used to create various content filtering policies, enabling you to apply different policies to different addresses of your network. If you wish to apply the same policies for every network in the company this can be done in Web Protection > Web Filtering. In addition, each filter profile can have its own user authentication method.
Multiple filter profiles allow you control authentication and web content for different networks. For example you can have a set of policies for your corporate computers using AD SSO, and a different authentication method and set of policies for a guest wireless network.