A summons is a paper issued by a court informing a person that a complaint has been filed against her. It may be served by a sheriff or other authorized person for service of process, called a process server. The summons states the name of both plaintiff and defendant, the title and file number of the case, the court and its address, the name and address of the plaintiff's attorney, and instructions on how to file a required response to the complaint within a certain time (such as 30 days after service), usually with a form on the back on which information of service of summons and complaint is to be filled out and signed by the process server.
A copy of the summons must be served on each defendant at the same time as the complaint to start the time running for the defendant to answer. After service to the defendants, the original summons, along with the "return of service" proving the summons and complaint were served, is filed with the court to show that each defendant was served.