A charging document is a pleading that initiates criminal charges against a defendant. It—not arrest—signifies the commencement of a criminal case. Complaints, informations, and indictments are charging documents.
Typically, when officers make an arrest, they draft reports, then present those reports to the prosecution. The prosecution then decides whether to file charges against the arrestee. There are, however, instances in which an arrest may follow the filing of a charging document. For example, a grand jury might indict a defendant, after which point the authorities take him or her into custody.