In wiki parlance, a user page is an article outside the thoughtspace of the wiki itself, primarily for two purposes. One, to give editors a “scratch” area to develop articles and try out wiki technology before dabbling in the main namespace, and two, for editors to set up a small “about me” page that engenders a sense of community in the wiki. A collection of fun templates have been created for the latter.
Unlike in the main namespace, in the user space the MediaWiki software treats “/” characters as hierarchy divisions. This allows you to set up and organize “areas” for different projects you may be working on.