An Illinois Summons is a legal document issued by the court that requires someone to appear in court for a hearing. There are two main types of Illinois Summons: a summons to appear for a trial, and a summons to appear for a hearing. The trial summons informs the defendant of the charges against him or her, and the hearing summons is issued to witnesses or other parties involved in the case. The summons must be served to the defendant, either in person or by mail. Once served, the defendant must appear in court on the date and time indicated on the summons. Failure to appear may result in a warrant being issued for their arrest.