A WikiProject is a section in the current wiki gathering pages relating to a mapping project, usually for a particular country/territory.
The "WikiProject" page name prefix was used for these pages since the early days of OpenStreetMap, and is something we're stuck with. See Wiki guidelines#Titles - Page naming convention Talk:Wiki organisation
WikiProjects can have subpages storing information available in the scope of the entire project using a set of templates. For example for WikiProject France, the params subpage has the following information stored, name: France, lat: 47.14, lon: 3.21.
The param subpage stores slash separated common informations.
Those informations are, in order :