Light tab: Shows all of the currently defined lights. An initial list of default lights can be created when you first enter draft or quality render mode. The 
symbol indicates whether the light is turned on. The 
symbol indicates whether the light indicator will be displayed.
Edit: Click to open the Properties window for the selected light. See Editing Lights.
Delete: Deletes the selected light.
New Light: Click to add a new light. The Light Parameters window appears, in which you can specify the light type and parameters. For details on the parameters, see Editing Lights.
Show All: Displays all light indicators. Hide All: Hides all light indicators. Restore Defaults: Returns to the initial default light set. New lights will be deleted, and modified lights will be reset to their original settings.
...