AD stands for Anno Domini. The term Anno Domini is a Medieval Latin term which literally means "In the year of the Lord". It is used to label or number years in the Julian and Gregorian calendars. Sometimes C.E. (Common Era) is used instead of "Anno Domini", by Non-Christians.
There is a common misconception that AD specifies "After Death" which is totally wrong. This misconception is occurred due to BC because BC stands for Before Christ. We are living in the AD era. So, every date containing year is added with a suffix AD.