If you're a fan of horror movies, or just movies in general, chances are you've had this experience: You settle down in your theater seat, excited to see the latest film from Quentin Tarantino or Guillermo del Toro, and then about ten minutes into it, you suddenly realize that your favorite director didn't have anything to do with the movie at all despite the fact that his name is on all the advertising. You've been hornswoggled!

Welcome to the shady and mysterious world of "presented by."

Opening in theaters this week is a new horror film by the name of "Mama," directed by Andres Muschietti. "Mama," which is about feral children who have an imaginary guardian, is a feature-length adaptation of Muschietti's own short film of the same name. Safe to say it's a labor of love for Muschietti, especially since it was co-written and produced by his sister Barbara.

Well, the short answer is that usually it just means they watched the movie. Yes, the presenters are often listed as executive producers, but often the only thing they actually produce is enough clout to get the movie shown in theaters by attaching their name to it. The most famous example of a presenter in this vein is, of course, Quentin Tarantino. In 2001, Tarantino helped launch this whole phenomenon with "Iron Monkey," which was released under his name and went on to earn over $14 million in America. But he didn't actually work on the movie; he just liked it so much when he watched it that he brought it to American distributors.

The same is also true of 2004's "Hero," which debuted at number one at the box office and racked up over $53 million dollars. That movie was actually made in China in 2002 without QT's involvement; once Tarantino threw his weight behind it, though, it got a theatrical release stateside. Hey, don't forget that before he became a moviemaker himself, Tarantino used to be a video store clerk, so recommending movies is something he does really well.

Of course, some other directors who champion smaller movies also take a more hands-on role. Robert Rodriguez, for instance, helped produce 2010's "Predators," which is why the film was advertised everywhere as "'Predators' presented by Robert Rodriguez," even though the movie was actually directed by Nimród Antal.

The bottom line, though, is when you see a movie like "Mama" with the name of one of your favorite directors attached, just remember that chances are they didn't direct it or write it or even really produce it — they just believe in it enough to put their name on it.

The question is, how much do you trust them?