Can you tell me about Facebook friend features?

[Jenna]

If you can no longer see someone in your friends list, it means they deleted you. That's how it works: the other person doesnt get notified of this. If you can't even find them when you search, they may have deleted their account altogether.
The Newsfeed is a compilation of things that your friends have been up to, but it's not entirely random. Facebook will select content from friends who you commonly view, chat with, or comment on. You can manually adjust this by picking which friends you are "subscribed" to, by pressing the button at the top of their profile page.