If you add a user to your Ignore List, you are unable to see their posts e.g. If you don't like reading BabyBoy's posts, you add him to your Ignore List and you will not see his posts or receive PM's from him.
*mmm* That sounds like a good idea to me.
Your Buddy list is a little different. If you have users on your Buddy List you can see if they are online when you open your User CP. You are also able to send group messages to all your Buddy's on your list. They are not really that special in my opinion.
1. Click on User CP (Right under the advertisement at the very top)(Here is where you see your Buddy List)
2. Click on either Edit Buddy List or Edit Ignore List (Right above the New Private Messages box)
3. Type in a name in appropriate list
4. Click Update List
I'm not treating you like you're stupid, that's just the way I explain things