Facebook groups have become very popular in recent months, it is a useful tool that allows users to interact on a common topic (or not). Following this growth, Facebook has decided to launch a specific application to manage and display only the updates of the groups you participate in.
With the app you can create groups, change your information, receive notifications and discover new groups of interest, that is, everything that the main Facebook app should do.
The app is already available for iOS and Android. (In case you're interested.)