Suspend To RAM
You can configure your PC to turn off all components but the main RAM memory.
So the motherboard will keep only the RAM memory receiving energy and keeping all other components turned off, making your PC to consume only 5 W. The advantage of this state is that when you ”wake up“ your PC it will be on the same status it was when you put it to ”sleep“, i.e. keeping the same programs and documents opened, for example.
You can even program your PC to perform tasks while it is sleeping: downloading e-mails, for example (the PC ”wakes up“, executes the programmed task, and then goes back to ”sleep“).
Some motherboards have a connector called STR that allows you to install a LED that will be turned on when the PC is in STR mode.
This feature is largely used by laptops to save battery life.