Kathleen, A.D. stands for the latin phrase "Anno Domini", which means "The Year of Our Lord (Jesus Christ)". It referes to the time after the birth of Jesus Christ. The year 2010 A.D. means that we are living 2010 (two thousand ten) years after the birth of Christ.

Yes, it means "Anno Domini".

Mister Wright is spot on. In Chinese, A.D. is 公元