Lit temporarily hides the Application Menus, like File, Edit, and others. When you're done, it quickly restores them so you can continue working.
By hiding the menus, menubar apps that were behind them become visible and usable. No more fiddling with overlapping menus while trying to find the right item.
Some menubar apps use techniques that interfere with Lit. As we find them, Lit will automatically update itself to ensure seamless operation.
Go here for detailed instructions.