A warrant is generally an order that serves as a specific type of authorization, that is, a writ issued by a competent officer, usually a judge or magistrate, that permits an otherwise illegal act that would violate individual rights and affords the person executing the writ protection from damages if the act is performed.
A warrant is usually issued by a court and is directed to a sheriff, a constable, or a police officer. Warrants normally issued by a court include search warrants, arrest warrants, and execution warrants.