When you are done working with your computer and is ready to go home, you should always log out or completely shutdown your computer. The difference between logging out and shutting down is that when the computer is shutdown it does not use any power but the effect is the same as logging out.
By logging out or shutting down your computer you make the following possible:
Sometimes you are offered the choice of “Update and shutdown”. This will happen when the computer have important updates to install. This option is recommended. If you have been offered this you should select it, you wont have to do anything else, the computer will shutdown when its done.