NightWing is the grown up version of Robin. He becomes NightWing after joining the Teen titans. But he only joined TT because Bats dropped him!! And he still got two other Robins!! It's so screwed up!!!!!
alright nightwing is dick grayson who was the first robin he left cause he wanted to break out on his own so tim drake took dick's place as robin but now tim goes by red robin jason todd was a loose cannon that's why he's never mentioned on the show then there's damian wayne who i believe is bruce's son or foster son so now damian is the new robin in the comics
'Robin' is an alias used by several characters.
In the Young Justice universe, 4 to be exact.
The 1st Robin - the one in season 1 of YJ - is Richard "Dick" Grayson. He's Nightwing in the second season.
The 2nd Robin - Jason Todd, was killed by the Joker sometime after Dick became Nightwing. When Jason was ressurected he became Red Hood (not in Young Justice)
The 3rd Robin - Tim Drake is the one you see in Young Justice season 2. He becomes Red Robin in the future.
The 4th Robin - Damian Wayne, Bruce's biological son. His mother is Talia al Ghul, Ra's al Ghul daughter. Yes, he's Ra's' grandson.
I'd recommend watching 'Batman: Under the Red Hood' to learn about Jason. And 'Son of Batman' for Damian.
And also 'Batman: Bad Blood' just 'cause it's so effin' good.
And 'Justice League vs. Teen Titans'.