What's the purpose of the "thumbs up" and "thumbs down" on threads?

It is to help people find useful and/ or interesting threads. (Also, if you thumbs-down a post, it collapses it from your view, so you don't have to see it again.)

if you like a post you thumb it up, if you don't you thumb it down, thumbed downed threads disappear for the one who thumbed it down, it's like a mini ignore

So we don't have to see you again.