What will happen if you turn your PS3 off?

If you turn off your PS3 then it will turn off can't get more simpler than that.

You should turn your PS3 off when not using it. It is not like a PC where you leave it on. You should know that the USB will no longer charge your controllers if it is off. ( One reason people purchase charging stations) It is advisable to set the controllers to automatically turn off when the PS3 is turned off or you will always find your controllers have no charge. The settings menu for the PS3 has auto shut off settings for both the PS3 and controllers and both should be set to turnoff automatically.