When you divorce your spouse, the court requires some guarantee that he knows you're doing it. All citizens have a constitutional right to defend themselves when someone is suing them and to take an active part in the litigation to ensure the court hears their side of the story. This is due process of law.
Serving Your Spouse
After you file your divorce petition, you must make sure your spouse receives a copy. Your options for doing this depend on where you live. For example, in North Carolina, you can send him the paperwork by certified mail. When he signs for it, you've achieved service and complied with due process requirements. Other states, such as Illinois, don't permit service by mail, but you can hire a private process server or the local sheriff to personally deliver your documents. If your divorce is amicable, most states allow either your spouse or his attorney to sign for the paperwork, voluntarily acknowledging receipt. If you can't locate your spouse, most states allow you to post a notice in the newspaper to achieve due process, but this often requires special dispensation from the court.
Due process also addresses the issue of jurisdiction. Courts require jurisdiction before they can make decisions regarding you, your property and your children. When you file your petition, this gives the court jurisdiction over you. When you serve your spouse, it gives the court jurisdiction over him, so your divorce can move forward.