The Configuration tab is where project or task statuses and task priorities can be defined. The project management module comes with a predefined set of these items. This tab may only be accessed by users belonging to roles with the Manage configuration permission for the project management module.
More resources can be found in Developer's Guide -> Modules -> Project management -> Overview.
Page url: http://devnet.kentico.com/docs/5_5r2/contexthelp/index.html?pm_configuration.htm