A more thorough explanation:

Service of process is a legal term that refers to the act of delivering court documents to a defendant in a lawsuit. The United States Constitution requires that defendants have proper notice of court proceedings in order for the court to have jurisdiction over them.

When a plaintiff files a lawsuit, they must arrange for the defendant to be served with a court summons and a copy of the complaint. This is called process. The summons and complaint must be given directly to the defendant or left with a suitable person at their home or place of business. It is usually done by an adult who is not a party to the lawsuit, but professional process servers can also be hired.

For example, if someone is suing their landlord for not returning their security deposit, they must arrange for the landlord to be served with a court summons and a copy of the complaint. This can be done by hiring a professional process server to deliver the documents to the landlord's home or place of business.

There are exceptions to the general rules of service of process. For instance, defendants can waive in-hand service of process, which means they agree to receive the documents by mail instead of in person. If they refuse to waive in-hand service, they must compensate the plaintiff for the costs of arranging for in-hand service.

Rules governing service of process vary by jurisdiction, so it's important to consult the state civil procedure rules for specific requirements.