FILL-IN-FLASH

If you have pictures where the foreground is too dark while the background seems to be correctly exposed, then using fill-in flash will make the picture look better.
You usually use fill-in-flash when you are in the shadows and shooting through objects in the foreground that are acting as a frame.
In the pictures the background is bright from the sun, but our faces are darker from the shadows, fill-in-flash lightens up our faces so you can see them better.