This is the default state and indicates the project is active.
This state removes the projects from the scheduler and timesheets. You can still generate report data on them.
Pending / Planned / Floating
Each of these statuses have their own project group allowing you to move projects between the groups dynamically by setting a different status on a project. If you want to make your own status, you are best using Project Custom Fields in conjunction with Smart Groups to achieve the same effect but with your own labels.