What is the difference between CE and AD?

There is no difference in dating, just in the terms and who uses them. Anno Domini is Latin for "in the year of the Lord" referring to the birth of Jesus. C.E., the abbreviation for "Common Era" is used by Jews and other non-Christians to refer to the same system of reckoning, which has become the basis for the civil date in much of the world. In the same way, B.C.E. "Before the Common Era" substitutes B.C. "before Christ."