An "annulment" is a statement that, even though a marriage existed historically, it was not sacramental and, therefore, did not give rise to the "till death do us part" dimension
of Christian marriage. Any person who has been married previously must have such an annulment declaration before entering a marriage in the Catholic Church, regardless of whether
that person is Catholic or not. Annulments are processed by the Metropolitan Tribunal of the Archdiocese of Atlanta
That site will give you a wealth of information about the process and will answer most of your questions. Any of our clergy
or case sponsors will be
happy to provide you with more details.
Where an annulment is applicable, no marriage may be scheduled until the final decree is issued.