The Guardians of the Galaxy is a group of heroes who opposed the Phalanx conquest of the Kree system (and many who had opposed Annihilus' incursion into their universe), and banded together in an attempt to prevent any further catastrophes from ever occurring.
On the recommendation of ally Nova, the group established a base of operations at the space station Knowhere, which conveniently possessed a teleportation system with near-universal range. An intelligent, super-powered dog called Cosmo acted as Knowhere's chief of security and worked closely with the new team during their first missions.
After an initial clash with the revitalized Universal Church of Truth, the team's investigation of a mass of "Limbo ice" revealed a semi-amnesiac man who identified himself as Vance Astrovik, a.k.a. Major Victory of the Guardians of the Galaxy of Earth-691. Astro's declaration inspired the as-yet-unnamed team to adopt the "Guardians of the Galaxy" name for their own.
Further Reading Marvel Wiki
Rocket & Groot