Rock Lee (a.k.a. thick eyebrows, as Naruto calls him) is a genin level ninja. at the beginning of the series Just like his row model Gai-sensei, he is a TaiJutsu specialist. Lee is incapable of using NinJutsu or even GenJutsu. But due to Lee's great determination and extreme hard work, he was able to counter this great weakness by specializing in Taijutsu.
In Lee's schooldays everyone thought he would never be able to become a ninja, simply because he can't use NinJutsu and GenJutsu. But Lee has great determination, and said to himself that he could be a very strong ninja that only uses TaiJutsu. That's when he met Gai-sensei. Gai is also a ninja that only uses TaiJutsu. Gai-sensei became Lee's teacher and row model, and he taught Lee everything he knows now.
Lee also has a crush on Sakura. At first Sakura didn't want anything to do with him because he looks weird. But after saving her life and the fight with Gaara, she is starting to see what's so special about him: his unstoppable determination. Lee's training consists of physical training only. He always wears extremely heavy weights around his ankles. Lee only takes them off in life and death situations. When he does this he speed and strength increase dramatically. But Lee's true power lies in the fact that he can open several of his body's chakra Gates. After opening several of his Gates he can temporarily posses even more chakra then the Hokage, which makes him inhumanly fast. The downside of this technique is that it does severe damage to his body, that's why Lee can only do it for a very short time. If he can't finish his opponent before his body receives to much damage, he's done for.