The Gobi is a large desert and semi-desert region spanning in southern Mongolia and northern China. It's about 1600 km (1000 mi) wide and 1000 km (600 mi) long, and is bounded by the Altai mountains and steppes of Mongolia on the north, the Tibetan plateau to the southwest, and the North China plain to the southeast. The word gobi actually means desert in Mongolian, so the common English rendition ("Gobi desert") is a redundancy.
The Gobi, as its name implies, tends to be very dry, characterized predominantly by rocky outcroppings surrounded by gravel plains, though it incorporates mountainous areas as well. The predominant plant life consists of drought-resistant shrubs and grasses that can thrive on the minimal summer rain and survive even the cruelly cold winter months. The temperatures range from an average of about 20°C during July to around -30°C during the January, though the actual highs and lows can be much more extreme, and the temperature can fluctuate as much as 30°C in a single 24-hour period.
The Gobi is well-known among paleontologists, thrilled that the recent thawing of relations with the west has allowed them to travel study the plentiful dinosaur fossils firsthand; the first dinosaur eggs ever discovered come from the Gobi. And varied animal life exists today in this harsh environment. The wild horse or takhi is native to the Gobi, though little seen there today. On land are jerboa, small nocturnal mice-like animals; a species of wild ass; various species of lizard; ibex; and the endangered snow leopards, a species ofwolves, and a species of bear. There is also a little-studied native camel, largely supplanted by domesticated camels kept as beasts of burden by nomads; they have also introduced herd animals such as sheep and goats, from which they shear cashmere wool. These livestock, unfortunately, have endangered native grasslands.
Want to know more?
http://www.oneearthadventures.com/gobi/wildlife/wildlife.htm has nice write-ups on several of the native animals in the area
http://baatar.freeyellow.com/ contains links to many articles - a good number in Mongolian - about the culture of the people who live in the region
http://en.wikipedia.org/wiki/Gobi_Desert has lots of detailed information about the ecology of the Gobi
The Story of the Weeping Camel is a lovely documentary set in the Gobi that shows the beauty and harshness of the area and something of how the nomadic herders live