When their race was overcome in a war with the Goa'uld, a small group of men were selected to leave their planet and search for allies. After failing to find anything but more hardship, they chose to desert the rest of their race and hide out on Earth.
Only one in this group listened to his conscience: Martin Lloyd. He believed that he and the others were responsible for their actions and should return to their world. Instead, the others gave him Earth drugs to suppress his memories of his true identity as an extra-terrestrial.
Martin's race possesses technology far advanced from Earth's. They are obviously capable of space flight, and are in possession of very sophisticated equipment, possibly on a level similar to the Tollan.
Martin, having temporarily uncovered who he really was, provided the S.G.C. with the Stargate address for his homeworld. After arriving on the other side it was clear that, from the vantage point of the Stargate, the Goa'uld had succeeded in annihilating Martin's entire civilization. Martin returned back to Earth to live out his life.
Martin's comrades got their chance to eventually beam away to their approaching mothership, leaving him behind on Earth. But it's what he wanted, as Lloyd has a new purpose: the sci-fi TV show Wormhole X-Treme!
Point of No Return - SG-1 learns that a group of aliens are hiding out on Earth, as deserters from a war their people were losing to the Goa'uld. When they visit Martin's homeworld, they discover that the Goa'uld have wiped out the civilization.
Wormhole X-Treme! - Tanner and his men leave Earth on their ship, which was programmed to return for them. Martin stays behind, as a TV producer.
200 - Martin visits Stargate Command to get ideas from SG-1 on his Wormhole X-Treme! feature film script.