Generally, a "writ" is a written judicial order authorizing a specific act. Historically, the parties to the litigation had to apply for and obtain many writs during litigation. Modern litigation has done away with many of the historial writs, but a few are still in use. Some writs relate to pre-trial matters (e.g. writ of attachment), some related to enforcement of a judgment (e.g. writ of execution), and others may deal with appellate law (e.g. writ of review). A few examples are discussed below.
Writ of Execution
Writ of execution is perhaps the most commonly encountered writ in civil litigation. After the court has entered a money judgment in favor of a party, that party may apply to the court clerk for the issuance of a "writ of execution". This writ authorizes the Sheriff of a specified county to seize the assets or the wages of a judgment debtor, and turn them over to the judgment creditor in satisfation of the judgment. This area of law is governed by Sections 699.510, et. seq., of the California Code of Civil Procedure.
Writ of Attachment
California law allows certain plaintiffs to apply to the court for a "writ of attachment", to take a lien on defendant's property before the case goes to trial. The basic requirements are that plaintiff has a claim for a sum certain amount of damges (such as a collection action), and plaintiff proves to the court the "probable validity" of her claim. If the judge is satisfied with plaintiff's application, the plaintiff must post an undertaking (a civil bond) before the writ of attachment is issued. A plaintiff may apply for a writ of attachment by way of a noticed motion, or in proper circumstances by ex parte motion. This area of law is governed by Sections 488.010, et. seq., of the California Code of Civil Procedure.
Writ of Mandate
A "writ of mandate" (also known as a "writ of mandamus") is an order issued by any court to a lower tribunal, corporation, board or person, to compel the performance of an act which the law specifically enjoins. The party applying for a writ of review must verify his application under penalty of prejury. This area of law is governed by Sections 1084, et. seq., of the California Code of Civil Procedure.
Writ of Review
A "writ of review" (also known as a "writ of certiorari") is an order issued by any court when a lower tribunal or officer has exceeded its jurisdiction in exercising a judicial function, and there is no appeal or judgment of a court that may provide a plain, speedy or remedy to the aggrieved party. A writ of review can be issued where there is no plain, speedy and adequate remedy in the ordinary course of the law. The party applying for a writ of review must verify his application under penalty of prejury. This area of law is governed by Sections 1067, et. seq., of the California Code of Civil Procedure.
Additional resources provided by the author
The body of law surrounding writs is very vast. For additional information, you may refer to California Practice Guide: Civil Procedure before Trial (published by the Rutter Group), California Practice Guide: Enforcing Judgments and Debts (published by the Rutter Group), or the California Code of Civil Procedure.