4413217e_mera_modes_for__anyway____CNET__Description
[Mode] Backlight [Uses] Any shot where there's a lot of ambient light but the subject is in shadow. [Description] 
Because a camera's automatic exposure is based on an average scene brightness, shots with a light source behind the subject will think there's more light than there is and produce a too-dark shot. This mode compensates for that, sometimes by turning on the flash.
What are all those camera modes for, anyway? - CNET