There are two species of Camels, the one humped, or dromedary camel of North Africa and the Middle East, and the two humped, or bactrian camel of Central Asia. Bactrian camels have been used for trade and transportation in Cental Asia for thousands of years. In Mongolia camels are one of the 5 main domesticated animals along with horses, goats, sheep and yaks. Camels are and were during the Mongol Empire mainly used for transportation and dairy products. Camel milk and yogurt are good sources of calories and remain popular in modern day Mongolia. In terms of transportation Camels were mostly used to carry heavy loads of trade goods or when migrating. When a Mongol Nomad decided to migrate as they did around 4 times a year they would pack up their ger and use camels drawn carts to carry the ger pieces and other supplies to the intended location. For the Mongols horses were the primary mode of combat and I am not aware of any examples of Mongols riding camels into battle, though that does not mean it did not happen.

Info from "The Mongols by David Morgan"