The Prosecutor, in Canada, is called a Crown Attorney. The job of a Crown Attorney is to prosecute the criminal charges laid by police officers. This is an adversarial process. The Crown tries to prove you committed a criminal offence, and as the defence attorney, I try to prevent that, on your behalf. The Crown is the state’s lawyer, and I am your lawyer. It is the state against you. Note that the victim/complainant does not have a lawyer. The role of the victim in this process is that of a witness. It is therefore, the Crown who decides whether or not the prosecution proceeds, not the victim/complainant.
Crown Attorneys are quasi-judicial officers. This means that they have an obligation to act fairly. It is said that the Crown never wins or loses a case. The obligation of the Crown is to prosecute every charge or case that has a “reasonable prospect of conviction” and is in the public interest. Conversely, it is the obligation of the Crown Attorney to withdraw cases from prosecution when he or she comes to the conclusion that either there is no reasonable prospect of conviction or that is not in the public interest to proceed.
The Crown advances the public interest and I advance your interest.