Most civil lawsuits start with filing a Complaint. The Complaint is a document that describes what the Plaintiff wants and why. At the same time the Complaint is filed, the court clerk will issue a Summons. The Summons provides the Defendant with important information including the deadline to respond to the Complaint.
After the Plaintiff has filed the complaint and the clerk issues the summons, the Plaintiff must serve these documents on each person/entity being sued (defendants). After the Defendants have been served, they typically have 20 days to respond. If a response is not filed within the required time period, the Plaintiff can request the court to award a default judgment.