1. Short for Power Supply and sometimes abbreviated as PSU, which is short for Power Supply Unit. The PS is an internal hardware component used to supply the components in a computer with power by converting potentially lethal 110-115 or 220-230 volt alternating current (AC) into a steady low-voltage direct current (DC) usable by the computer. A power supply is rated by the number of watts it generates. For example, the image to the right, is of an Antec True 330, a 330 Watt power supply and an example of what a computer power supply looks like.
Caution: Do not open the power supply, it contains capacitors that are capable of holding hold electricity even if the computer is off and unplugged for a week, if not longer.
On the back end of the power supply as shown in the above picture is where you connect the power cord to the computer. On the front-end, which is not visible unless the computer is opened is several dozen other cables that connect the power supply to each of the devices and the computer motherboard. With many PC computers today the power supply connects to the motherboard using an ATX style connector, other connectors include: Auxiliary connector, Berg connector, Molex connector, and P4 connector.
2. Linux command, see the ps command page for further information.