Documentaries tend to do exactly what their name implies- document some aspect of our lives, typically to illustrate a point or profile a particular person, event or era.
This often dry yet information rich form of cinema has proven to be an extremely effective way to sway the public opinion, making soapboxers seem like champions of justice.
And yet sometimes soapboxing is a good thing, as it demands people pay attention to an issue in need of repair, which is when documentaries can actually make a difference in the world.
Remember Blackfish, the documentary that made Sea World's stock plummet? Love or hate the message you must admit the film made good points, and it forced Sea World to change their practices for the sake of mammalian sea life.
The Cove similarly shed light on the fact that dolphins were being slaughtered in ridiculously high numbers for no good reason, and since the film's debut the number of dolphins captured annually in Japan has dropped by 75%.
But documentaries don't just save animal lives- The Thin Blue Line helped free Randall Dale Adams just days before he was set to die by lethal injection for the murder of a police officer that he didn't commit.