My apple computer screen is black
Why is my computer screen black but I hear it turn on ?
Then it sounds like either your GPU has failed, the backlight on the display has failed or the display itself has failed. IF you have an external display, please connect it, if it works your GPU is fine. Either way though it sounds like you need to take it to your local Apple Authorized Service Provider to be properly diagnosed.
Before doing so, try to reset the NVRAM and also try to restart in Safe Mode.
How to reset NVRAM on your Mac & Use Safe Mode to isolate issues with your Mac