A writ is commonly endorsed or delivered by a sheriff (who may be instructed to seize property, for example) or as a notice to a defendant (for whom the writ is the first notice of formal legal action. In these cases, the writ would command the person to answer the charges laid out in the suit, or else judgment may be made against them in their absence).
Some jurisdictions may prefer the term summons, citation or even notice.1
In Painter v. Berglund, Justice Ward of the California Court of Appeals wrote:
"A writ is an order in writing issued by a competent official in a judicial proceeding and, as applied to execution in civil cases, is part of the remedy to effectuate the action by the enforcement of the judgment."
The writ has a long history in the English common law as the formal document by which the machinery of the courts of law were put in motion and directed to a person, the defendant, by the plaintiff. The endorsement of the writ was done personally by the seal of reigning monarch and later, by his agent on his (or her) behalf and, more recently, by the clerk of the issuing court. The writ directs the named recipient to do something, usually to answer the allegations or suffer judgment in absentia.
Circa 2012, here is the still archaic form of a writ in one jurisdiction:2
"ELIZABETH THE SECOND, by the Grace of God, of the United Kingdom, Canada and Her other Realms and Territories, Queen, Head of the Commonwealth, Defender of the Faith.
"To the defendant(s):
"TAKE NOTICE that this action has been commenced against you by the plaintiff(s) for the claim(s) set out in this writ.
"IF YOU INTEND TO DEFEND this action, or if you have a set off or counterclaim that you wish to have taken into account at the trial, YOU MUST....
As the law evolved, it became necessary for the plaintiff to specify the basic facts behind the writ, either directly within the writ, or in a companion document such as a statement of claim.