An annullment is similar to a divorce and terminates the marriage relationship,  but after it is granted it is as if the marriage never existed  in the first place.

We all of us find out things about our new partners after we get married !  Sometimes they are just minor facts that we need to adjust to but occasionally they are facts that totally change the validity of the marriage.

Questions such as : 

Was either partner married to someone else at the time of the present marriage?

Are you or your spouse closely related?  Brother/sister etc.

Do you or your spouse have any long standing mental illness which would mean that you were not capable of understanding the committment?

Were either of you Forced into this marriage? (undo duress)

Is one of you physically unable to engage in sexual intercourse or not willing to try or change?

Have you failed to consummate the marriage?

Were either of you to young by law to enter into marriage?

Did either of you not get your parents consent (if it was required because of age?

Was the wife pregnant with another mans child at the time of the marriage?

Did one of the parties grossly misrepresent themselves at the time of marriage? (criminal history /religion etc)

Did you fail to meet the necessary legal requirements? (no witnessess etc)

If you or your partner can answer yes to any of the above there is certainly a possibility that you can apply for an annullment instead of a divorce.