Safe mode is a mode of startup in computers that allows the user to detect and fix errors. Many things don't run on safe mode. The purpose is to see whether any of the recently added or updated device drivers were causing the problem.
When safe mode is used, a computer will only start with the minimum number of system files needed for it to work properly. This is to make it easier to find a problem that may be causing a computer to work incorrectly. The screen resolution is also smaller and there is no sound or internet connection in safe mode. This is because these features are not necessary for the computer to work properly.