Usually, a beam of light falls from a light/bulb/ sun onto the object, whose light reflects and falls on our eyes. This light is then reflected on our retina, and we are able to see. But in the case of mobile phones it is a completely different approach. There are different mobile screens, namely LCD and LED screen. LCD screens consist of a panel of liquid crystal molecules. Electrical current is channeled through these monitors in order to create certain patterns. These patterns can either block light or allow it through, and that’s what creates the colors and details on your screen. hence the light is emitted from the phone screen itself, and itself contains the colour variations, which directly falls on our retina and makes it visible.
However LED phones, give off light of their own, and hence there is no need of backlight.
In summary, light from inside the display of the phone (backlight) or the light emitting from the LED screen itself, contains all the data, which falls on our eyes, to make it visible.