With a project, people collect content in a way that focuses their work along a schedule toward a specific goal. A project is a great way to give collaborative work a context that's time-based and outcome-based.
You can disable the projects if your community won't be using them. Disabling the project feature essentially means hiding project-related user interface elements. For example, Projects won't appear on the New menu, the Projects home page tab and Your Projects widget will not appear, and so on. If there are already projects in the community when you disable the feature, then those projects will become inaccessible -- essentially invisible. Project data, however, won't be deleted.
Note that if you do want to delete projects, you'll need to do it while they're still visible -- before you disable the feature.
Admin Console: System > Settings > Projects