The standby mode (also known as screen blanking) is one of three power-saving modes for the ThinkPads. In this mode, only the LCD screen (and the external monitor, if attached) is turned off in order to save power. You can enter this mode by pressingor by configuring your computer to enter standby mode automatically after a chosen duration of inactivity. To resume work from standby mode, press any key.
See How to make use of Power Management features to learn about getting standby mode and other power-saving modes to function on a Thinkpad running Linux.