Robin is a stupid little kid that thinks he is the far superior yet still stupid Fat Robin. Robin is basically a hero that wants to be cool but he FAILs miserably. There have actually been several people who tried to be Robin, but each one of them FAILed so a new one had to take the role. Despite this, no Robin has ever successfully done anything awesome. Ever.
The first Robin was Richard "Dick" Grayson. Grayson became Robin after some bad guys killed his parents. Batman had heard about this, and decided the only logical conclusion was to make him a superhero. Robin became a superhero and Batman instantly became cooler in comparison.
Eventually Dick realized Batman was stupid, and he left. Batman needed a replacement, so he found some random kid off the street: Jason Todd. Jason was set to be the only cool Robin, except for one problem. He was the stupidest kid ever. This is why Joker beat him to death.
Batman, ready to get another kid killed, found Tim Drake and made him the new Robin. Drake liked being Robin and they went on adventures together. But then Drake said "Holy capers Batman!" and Batman kicked him out.
SPOILER ALERT: The fourth Robin was a girl. Stephanie Brown was the fourth Robin. He could have made her Batgirl, but Batman did not like Stephanie so he made her a Robin instead. As we all know, anyone who becomes Robin is cursed forever. Sure enough Stephanie died. Oh, I guess I should have put the spoiler alert there, huh? Oh well.
Eventually Batman decided he was done kidnapping random kids and making them Robin. He had a son of his own and trained him to be Robin. We're not sure why Batman would subject his own son to this, but Batman has never been the smartest.
- He's not wearing any pants.