Q: What is an Annulment ?
An annulment is declaration by a Tribunal to the Church that a marriage never existed as a sacramental union according to canon law.
Q: What is the difference between an Annulment and a Divorce ?
A divorce is a dissolution by a civil court of an existing union; an annulment declares that there never was a valid union, despite appearances to the contrary. There are both civil law and Church annulments.