You can now gives a thumbs up to stuff that you see and like. Think of it as a way of "recommending" something to others.
When you see the green "thumbs up" icon, that means you can click on it to recommend it to others.
Currently, the only place where this is visible is in the tips area. For now, that's the only place where it will be present, while we're in this brief "beta test".
Later, I will expand it so you can give a thumbs up to a post in a thread that you may have found particularly useful or informative, as well as other places, too.
Later still I will expand it further so that other can view your profile and see what things you have given a thumbs up to.
Feel free to play around. Go to the tips area and give a thumbs up to a few of the tips!