Group Hatching is where the people who agree to one, get an egg/baby at the same time, They grow it up, Keeping the others updated on the growth, Some group hatchings are Towards the same goal (ie: type of adult) where as others just see what you get compaired to the others in the group.
Might I just say that there is a pinned, bolded topic at the top of this forum that explains what a group hatching is. This place is not for questions. I suggest you check that topic out.