You don't have a backlight "function" @ Max Collodi what you are taking about ? The backlight will light your screen with the informations you need. If you don't have a backlight you will never see your screen.
Many laptops have the ability to toggle the backlight on or off. Usually, a combination the "function" key and one of the "F" keys will toggle the backlight. Laptops have this ability to save battery usage. There are situations where you may want to use the laptop and don't require use of the screen. Downloading files or listening to music while you are away from the computer are two examples. If your backlight is not working, this is the first thing you check. If that is not the issue, then a mechanical or electrical problem is evident.