This is the address of a website where you can leave your address and invite people from other countries to go and stay in your house. At the same time, you can also ask people from this web to go and join them in their houses.
It seems that the webpage is a serious one, because after your experience as a guest in a house, you can comment about it and recommend others to go to that person’s house or not.
I think it is a good opportunity for those of you who want to travel cheap and meet new people. Good luck!