The Hab is short for "The Mars Lander Habitat," which is the name given to the artificial living quarters constructed on Mars before the Ares III mission landed.
Each Hab is specifically designed to house six astronauts for the period of 31 Mars days, or sols. They are stocked with supplies that have been sent to the red planet over the course of fourteen unmanned supply missions. Astronauts inside each Hab are protected from solar radiation exposure by the durable industrial canvas from which their living quarters are made. The Hab also has state-of-the-art life-support systems which regulate temperature, oxygen, and water.
In case of emergency, the Hab is equipped with back-up LED lighting as well as spare oxygen tanks. Moreover, secondary and tertiary communications systems ensure that communication can be maintained between the Hab and an MAV, or Mars Ascent Vehicle, in the event of something going wrong.