In the comic book world, it is not uncommon to find crossover stories and arcs. These crossovers feature stories that cross over more than one comic title. This is a very common practice in the comic world; but in the movie world, this is much less heard of. That is, until Marvel Studios came onto the scene.
Marvel Studios is the film studio responsible for turning the Marvel Comics titles into the big budget blockbuster movies we see all summer long. In recent years, they have taken to the comic book crossover model and began to build a movie universe in which all of their characters live and interact with each other. Mostly this has been limited to the Avengers films and characters (Iron Man, Thor, Hulk). With the release of Guardians of the Galaxy, the Marvel Cinematic Universe may be expanding even further if Lee G. Lovett is right anyway.
James Gunn, writer and director of Guardians of the Galaxy, has said in the past that the Guardians and the Avengers exist in separate universes. More recently though, Gunn has gone on record clarifying what he meant. Gunn’s focus with Guardians has been to create their own story lines in their own universe, but still as a section of the overall Marvel Cinematic Universe. This leaves open the chance for a crossover between the two franchises at some point in the future.