Here is a somewhat typical Friends Slider:
Each one of your Friends gets one. It's a small window into their world. There are two main tabs on the top of this slider: Watched/Rated and Queue. Both of these tabs present movies in order of activity, that is, the order movies were watched or rated, the order they were added to a Queue (or reordered in that Queue). As you all have noticed, the Queue slider is not in Queue-order. The logic is that I like seeing what has recently interested my Friend, what they just added, just discovered, just moved, just rated. I'm not quite as interested in what they have at the number 5 spot. What's at that spot also might sit around for some time. I like to see new stuff and this is the best way to reveal it.
But, of course, it's fun to know what's in their Queue too. What they have at home. (Well, if they have it at home, that will show up as a little notice on top of the box art in the slider [see photo in this para], but even so...) On the far left part of the slider is a little info about your Friend. Notice here are two bits of information that are also links (I've circled them in the top image in the first para). This shows the number of rated movies and the number of movies in the Queue -- but if you click on either, you go to your Friends' page. Here you can see their full Queue (in a presentation that will be much more familiar), or all their movie ratings. There is a drop down menu of variations on their movie ratings, and the one I like the most is "Movies in Common." (It is also the page you see if you click on their "% Similarity To You" back on the slider). This page shows their ratings of movies side by side with your ratings of movies that you have also seen. It's a quick way to gauge your taste similiarity for yourself, or to rate a bunch of movies if you haven't.
The sidebar you get with your Friends is pretty similiar to the one you get for any reviewer you want to check out - except you can't see reviewer's Queues. With Friends, you can.
I hope this clears up a few questions about these features. Let me know if this makes more sense or if you have further need of explanation.