What is the document called that starts a lawsuit?

The complaint is the initial charging document that begins a lawsuit. The plaintiff is the person suing and the defendant is the person being sued. The complaint lays out the parties names and addresses, the jurisdiction of the court, underlying facts of why there is a suit, the legal claims asserted in the suit and the relief sought by the plaintiff. Each statement in a complaint is given a number. Thus, a complaint is written in number form in different sections. This document is then served on the defendant. This is called service of process.