Final answer:
Anno Domini (A.D.) means 'in the year of our Lord' and is used to mark years after the birth of Jesus. Today, Common Era (CE) is used interchangeably with A.D. for a more secular framework, while Before Common Era (BCE) corresponds to Before Christ (BC).
Step-by-step explanation:
A.D., or Anno Domini, which is Latin for 'in the year of our Lord', is a term that was established in the 6th century by Dionysius Exiguus. It is used to denote years following the traditional date of Jesus Christ's birth, distinguishing it from B.C., which stands for Before Christ. In modern times, a scholarly alternative has been developed, known as the Common Era (CE) and Before the Common Era (BCE), to provide a secular and more globally inclusive dating system. However, the year designations are equivalent, where AD coincides with CE and BC with BCE. Furthermore, the dating term BP, or Before Present, is related to radiocarbon dating and indicates 'years ago' or years before the present.