What's the difference between a police informant and a whistlebl

Wildwood - What's the difference between a police informant and a whistleblower? Nothing. They are used and needed to help the American justice system. What happens if we make public all of our informants? Why is spying good for one system and not for all systems? When is questioning made a crime? Are we all to be zombies and just go along? Why bother educating everyone when only the rich and powerful rule? What is happening to "justice for all?"