It is a paid to write website. In the site you can write a blog post or small article (called bubble) about any topic and you can include any kinds of links. I think you earn based on the number of views to your bubble. So the more meaningful your article (bubble) is the better earning chances you have.
The minimum payout is 25$. There has been lot of confusion about the site and whether it really pays. It seems that some people get paid while others dont. This may be depending on the kind of articles posted and whether any content is plagiarized.
I have never tried it since I want to focus on 1-2 article writing sites only for long term revenue earning. HP seems best to me.