AD - Anno Domini
The term Anno Domini is Medieval Latin, which means "In the year of the Lord". It is used to denote the era of time. Sometimes C.E. (Common Era) is used instead of "Anno Domini", to avoid Christian references. AD and BC are the designations used to label number of years in the Julian and Gregorian calendars, with AD counting years after the start of the epoch, and BC denoting years before the start of the epoch.
Misconception with AD
It is due to BC which is an English shorthand of Before Christ, AD has been incorrectly concluded to After Death, which is actually wrong to use.