The flash icon in an iPhone’s camera is generally a variety of circular icons with a lightning bolt in it. Here are some following rules for it:-
1. When there is a cross through the flash on iphone icon, then it indicates that the flash is turned off.
2. When the flash icon is white in color and without any flash, then it indicates that the camera flash is on the auto mode.
3. If the flash icon is highlighted in yellow color, then it means that the camera will flash every time you take a photo.