When you follow users, you have access to the posts that they publish in their feeds. In private groups, a coordinator must confirm your request before you are allowed access to this group's posts, comments, etc. In public groups you have immediate access to the group.
The feeds you follow are displayed under My feed and the groups you follow under Groups. To stop following a user or group, click Unfollow in the user or group profile. Users who are following your feeds are displayed under Followers in your profile. Users and groups you are following are displayed under Following in your profile.