;A; You drew Tiiiiiiiiiiimmmmm~ *gross sobbing* Tim has always been (and will always be) my favorite Robin. To me, he IS Robin. He was the boy for whom the role was actually born, but the creators had to take time and learn and develop Dick and Jason before they could actually create the character for whom the role was born, and that character is Tim. And I don't know why, but for some reason, I've always had a MAJOR soft spot for him.
Because DC comics can't ever completely kill them off. Richard "Dick" Grayson was the first actual "Robin" in the world of Batman. Originally he was an orphan whose parents were killed because of sabotage and Bruce Wayne/Batman, took him in. Eventually he had a bit of an argument with Batman, and they parted ways for a while. Richard went off to see the world and train a bit on his own, and eventually returned to Gotham City as "Nightwing." Jason Todd was the second Robin, who was a random kid Batman caught trying to steal the tires off the Batmobile, and he took him in on a gut feeling. Jason wasn't as elegant a fighter as Richard (who has background as an acrobat,) but he was far more inclined to violence and he was rather unstable. Eventually he was killed by The Joker, but if you ever read the "Under The Hood" graphic novels/watch the "Under The Red Hood" movie, Jason comes back as the dangerous, bloodthirsty vigilante known as The Red Hood. Tim Drake is actually adopted by Bruce Wayne/Batman, and is the most like him in the sense he is already a skilled detective at a young age. Tim befriends Nightwing, and the two consider each other brothers. Eventually as he gets older, Tim becomes Red Robin. And I'm not going to get started on Damian Wayne, because I hate that little bastard and as far as I'm concerned, he shouldn't exist. AT ALL.
But yeah, that's why there's so many Robins. There have even been a couple of female Robins, in some versions of Batman stories.