Sorry for the late response.
Your user page is your own WEBPAGE!! Yes, your very own. You can use it to showcase yourself and all the work you have been doing. This is very important because, trust me, if you search for yourself on google after doing a good userpage, you may most likely have this page as the first. The only catch is that, you are not supposed to advertise any commercial programme/products on it. Remember also that, it is mainly to showcase your educational activities and personal self.
To create a sub-page from any page, go to edit mode, put a square bracket and a foward slash "[/", type the name of the sub page you are creating, and then cose the bracket.