You’re a friend when you connect with them, similar to that other network people know. 🙂 Following is when you’re no their friend but you want to see what they’re doing as well, but you’re not interacting with them on their feed in the same way.

There are some short emails coming out to help members get more from the website. @john.kempf will no doubt take note of this and explain in more detail.

Currently all forum posts are shown in the feeds as well as blog posts and links. The tabs on the home page allow you to see just what you want to see.
All Updates – everything that’s posted on articles and forums as well as your connections.
Likes – All the comments and posts you have liked.
Connections – general activity by those you’re connected to.
Groups – comments within the groups you’re part of.
Mentions – people who have mentioned you in a comment or post.
Following – people you’re following but not connected to as a friend – you can interact with them here.

I hope that clarifies things for you.