It's a blog run by a fan and you 'confess' opinions on the show and housemates etc, and they'll make a picture with a caption of your confession and post it to their followers which people can reblog and post on their blogs too, and their followers can reblog it from them and so on. You can say anything you want and they'll post it, just not excessive or over the top insults or anything. Not a lot of people are posting confessions so I thought I'd post it here to boost the blog's popularity
http://bigbrotherconfessionsuk.tumblr.com
It's based on
http://thestanconfessions.tumblr.com which is much more popular and has more of a variety of posts so you can more of an idea of how it works by looking at that too
You don't need a tumblr to post confessions. It's good cause it helps the show have more of a presence on social media (tumblr is really popular)