A writ is a formal written order issued by a court or other authority directing a person or entity to perform, refrain from performing, or submit to a specific action. Courts use writs to initiate lawsuits, enforce judgments, compel testimony, or review the actions of lower courts and government officials. Every major civil action begins with the issuance of a writ.
Think of a writ like a court's official letter that carries legal force: ignoring it is not an option.
Courts issue different writs depending on what is being commanded or reviewed.
In common law jurisdictions including the United States, United Kingdom, Canada, and Australia, writs have historically been the formal mechanism for starting civil actions. You file a writ with the court, and the court then serves it on the defendant. The writ puts the defendant on notice and establishes the court's jurisdiction over the dispute.
Modern procedural rules in many jurisdictions have replaced the traditional writ with a complaint, petition, or claim form. The substance is the same: a formal document that initiates the legal proceedings and states the nature of the claim.
Winning a lawsuit produces a judgment, not automatic payment. If the losing party does not pay, the winning party must enforce the judgment. A writ of execution gives you the legal authority to compel enforcement. Armed with it, a sheriff can levy on the debtor's bank accounts, garnish wages, or seize and sell personal property.
Judgment enforcement is often the hardest part of litigation. A solvent defendant who refuses to pay can be compelled through writs. A defendant who has genuinely no assets provides nothing to seize regardless of how powerful the writ is.
Sources:
https://www.law.cornell.edu/wex/writ
https://www.uscourts.gov/about-federal-courts/educational-resources/about-educational-outreach/activity-resources/what-does
https://www.supremecourt.gov/about/procedures.aspx