To turn Sloop on or off, choose one of the radio buttons Sloop On or Sloop Off. When the Sloop is off, the Sail is actually sleeping in the background without tracking the mouse, switching anything, or using any processing time. However, the Sail is still technically running which means that you can't delete it from your hard drive.
If you want to completely uninstall the Sloop Sail, either to get rid of it completely or to replace it with a newer version, you can either drag the Sail out of the Extensions Folder and restart your computer, or you can use the Kill Sloop menu command and then drag the Sloop Sail to the trash and delete it. For more information, see the help topic for the Kill Sloop command.