Green Arrow has been a long running character in DC comics, ever since the 1940’s. It wasn’t until two decades after his debut and until 2007 his origin story was expanded upon. As with many comic book heroes his origin story has been expanded upon and revised several times.
The general background story is that Oliver Queen was a wealthy playboy and CEO of Queen Industries. He was wild, reckless and an alcoholic, living a hollow existence of luxury. Oliver Queen was orphaned at a young age when his parents were killed on a safari in Africa by lions. Oliver Queen blamed himself partly for their deaths, not wanting to use a weapon to kill the lions. After that incident he was no longer hesitant to kill animals in the future.
Oliver Queen started his training as a hero when he was marooned on an island after falling off (in some cases pushed off by his friend) where he had to survive for several months (or years depending on the source). He constructed a bow out of materials he found on the island and became an expert archer to hunt for food and survive. He also perfected many trick arrows that he would later use to fight criminals.
To get off the island, depending on the source comic, he either fought off pirates/druglords and took their boat or was found on the island by chance. The modern show “Arrow” takes a slightly different take with him being marooned on an island with mercenaries, former special forces members (such as Slade Wilson), Shado and her father.
After returning from the island and with his new found skills he put them to use to fight criminals. Despite running a billion dollar industry, Oliver Queen has always been the most left wing, anti-establishment hero of DC comics. In some origin stories he loses his company and his money due to inside corruption and finding out his company makes weapons.
Roy Harper, the sidekick with him from the beginning was an orphan as well. Having grown up on an Indian Reservation he was trained as an expert archer and hunter. When he joined up with Green Arrow he was called Speedy but later on when he went his own way would be called Red Arrow or Arsenal. Speedy eventually went his own way after dabbling in drugs and alcohol to the dismay of his mentor and partner Green Arrow.