What is the definition of private enforcement of laws?

This generally has to do with minor criminal actions like trespassing, noise violations, minor assaults, etc. Criminal laws are enforced by government prosecutors; however, some states permit private enforcement of those laws in certain minor cases. For example, if two neighbors start arguing and give each other a black eye, a prosecutor might not touch the case because it is a rather minor matter and they have bigger fish to fry. Plus, they are probably both blockheaded idiots not criminals. So, some states allow the persons themselves to file criminal charges against one another, thereby privately enforcing the criminal law. People doing this probably are blockheads, because if they win all that happens is the loser pays a fine to the State. Nothing gets paid to the winner. If they want money for damages for the black eye, the place to go to is civil court and sue on the tort of assault.