there is a gray screen with a dark gray folder with a lighter gray question mark inside it and i cannot use my mouse keyboard and the login screen doesn't appear

My mac has a light gray screen that appears when i turn it on with a dark gray folder with a light gray question mark inside the folder, this screen does not change i left it running to see if it would start up and it didn't and this is the only screen that appears, there is no login screen or home screen

PLEASE HELP!!!!