Prosecution is a verb which is derived from the noun prosecute. It is the act of being prosectuted or of prosecuting. Prosecution is basically being called upon to answer in court and under oath to an assertion made against a person which is contrary to common or criminal law. In the criminal court, the prosecution is the party that brings the charge against the defendant.
The prosecution team consists of the district attorney of the state (or sometimes a federal prosecutor) as well as the prison service or police service. The prosecution could be any attorney working for the US government.