[Brief Description] The highlighted tab indicates the current mode that Developer Tools is inspecting. Selecting a tab will also change the Mode-specific toolbar for this selected tab. [Reference Name] 
Mode tab
C o m m a n d M e n u b a r
M o d e t a b
M o d e - s p e c i f i c t o o l b a r
P r i m a r y C o n t e n t P a n e
P r o p e r t i e s P a n e
P r o p e r t y T y p e C h o o s e r