NO question is useless. However, the google definition of safe mode is the following:
Safe Mode - A temporary method of running Windows using the absolute minimum in resources. In the event of a hardware failure or malfunction, it can become necessary to run the operating system in the Safe Mode. In safe mode, it is sometimes possible to back up files and otherwise rescue data that is subject to loss due to eminent hardware failure. Windows is often able to alert the user to such problems before they actually occur. It would be wise to print out the instructions for Safe Mode operation prior to needing them. To do so, go to Start, Help, type "Safe Mode" into the keyword prompt box, click on Display and print the instructions for safekeeping.