A court clerk is a person who works at the court and helps the court to manage its affairs. Court clerks do things like file paperwork, keep track of cases, manage schedules, etc.
Court clerks do not prosecute crimes or hear trials. However, they are still vital to maintaining the ongoing operations of courts.
Court systems often have many, many files, as well as and a high volume of cases that they must keep track of. Without court clerks to do this work, courts could easily lose track of important information and confuse dates, appearances and trials. Court clerks make sure that the court can have all of its organizational and clerical needs met in order to operate at maximum capacity. This way, all of the trials and proceedings can occur in an organized manner, and files are kept track of.