There were 3 Robins, actually. First was Dick Grayson, the most famous. Second was Jason Todd (basically a Grayson clone - another circus kid whose acrobat parents were killed by Killer Croc), who was reckless and impulsive, and rather poorly-trained by Batman, resulting in Todd ending up dead by the Joker's hand. The third was Tim Drake, after Dick Grayson became Nightwing.

There actually have been 2 female Robins, as well, short-lived: Stephanie Brown (Tim Drake's girlfriend, after Tim's father forced him to retire from being a crimefighter) and Carrie Kelly (in an alternate reality).

It's official, I'm a dork and a Batman junkie.