When you log off from Windows, all of the programs you were using are closed, but the computer is not turned off.
After you log off, another user can log on without needing to restart the computer. In addition, you don't need to worry about losing your information if another user turns off the computer.
When you are done using Windows, you don't have to log off. You can choose to lock the computer or to allow someone else to log on to the computer by using Fast User Switching. If you lock the computer, only you or an administrator can unlock it.