The first popup menu, labeled Show option values, lists Global Preferences, Selected Notebook and Selection:
sets options for the entire front end
sets options for the whole notebook
sets options for the selected cells or characters in cells
Use this menu to choose the scope for an option. Some options are dimmed when they do not apply to the scope you have chosen.
The second popup menu lists options by category, alphabetically, and as text.
You can type an option into the Lookup text field to find that option in the Option Inspector. The Option Inspector goes to the first matching option. Press Enter to go to the next match.
Each line in the list of options gives the option name followed by its current value. Change the option's value by choosing from the popup menu at the right or by selecting the value itself and typing over it. A symbol in front of the option name indicates that the current value of the option is different from its default value.