A general term for a system that provides an astronaut with the necessary conditions for survival in space. These include communications and the adequate control of oxygen, temperature, pressure, humidity, and waste removal. Life-support systems are used to regulate the atmosphere of a spacecraft and for extravehicular activity (EVA). During EVAs, the system used is a portable device, also known as an extravehicular mobility unit (EMU), which is mounted as a backpack on the astronaut's spacesuit.

http://www.hq.nasa.gov/office/pao/History/alsj/plss.html Technical information, diagrams, and photographs of the Apollo spacesuit and the portable life-support system.