A WikiProject is a collection of pages that focuses on a specific subject within Wikipedia. It is not a place to write articles, but a tool to help others in writing articles. The talk pages that come with the projects are a useful forum for those who want to join a certain project.
Currently, Simple English Wikipedia is not yet large enough to have a large number of active WikiProjects. Many projects that have been created here in the past have been abandoned after a short amount of time. Because of this, WikiProjects are created in a user's userspace.
How to create a WikiProject
Anyone can create a WikiProject in their own namespace. Let's say you are user:Example and want to create a WikiProject about cars. You could create the page User:Example/WikiProject Cars for your project. You may then notify the community of your WikiProject on Wikipedia:Simple talk and list it on this page on the list of current WikiProjects below.