Jason Todd was the second Robin. Other personas in DC comics story lines for Jason Todd include: Red Hood (Batman #635 (February 2005), NightWing, Red Robin, Wingman (Batman Incorporated (vol. 2) #1 | July 2012), and in the 2015 video game Arkham Knight , he is revealed to be the Arkham Knight, a dark reflection of his mentor.
Read more about the DC comic book history of Jason Todd at the League of Comic Geeks site.
And on the Wikipedia page about Jason Todd.
