Kyle Rayner is the name that is associated to Green Lantern. This person is known to be one of the high-ranking members of the Green Lantern Corps. This means that he is one of the members of this extraterrestrial corporation. There came a time when the whole corps was destroyed and he was the only member who survived.
He had to get the ring in order to continue on what the corps has started. Take note that before he became part of the corps, he was a graphic artist and he did not know anything about the Green Lantern Corps at all. He started to acquire a lot of aliases the more involved that he became.