Access Control Lists are just what they sound like and yet they're so powerful and specialized that they're often misunderstood. In your initial post, talk about what you think they are now. Put the description in simple terms. After you have done some studying, return to the discussion and talk about how your thoughts have been validated or have changed since your initial post. If you have already studied ahead or know all about ACLs, talk about what you thought ACLs were all about when you first heard about them and before you studied. In your subsequent posts, talk about how your thoughts were validated or how theychanged from those first thoughts.