Rock Lee is a genin level ninja shinobi from the Hidden Leaf Village and a member of Team Guy. During his time as a student in the Ninja Academy, Lee proved to have no talent for ninjutsu and genjutsu. When Lee eventually graduated he was added to Team Guy. During the team's first meeting he vowed to become a splendid ninja that specialised in taijutsu. Neji Hyuga laughed at him, but their sensei, Might Guy, took a special interest in Lee. He encouraged Lee to keep at it and, in time, began teaching him powerful forms of taijutsu.
Through Guy's teachings, Lee has learned how to open 5 of 8 Inner Chakra Gates, a feat that is difficult for even the most talented ninja. Because of the danger to his body that the gates' power presents, Lee is only permitted to open them in certain circumstances such as life-or-death situations, protecting someone dear, or defending his way of the ninja. Most humans can only access less than 20% of their muscle potential but the eight gates uses chakra to "force" the muscles to work at much more power than they normally do, allowing the user to run at phenomenal speeds, pick up enormous weights, and much more at the expense of the muscles themselves.
If Rock Lee did that to anyone else, that person would likely be dead. Gaara was lucky to avoid any serious harm.
thumbs up for this masterpiece