Kakashi is one of the Hidden Leaf Village's "Jounin" (elite/top-level ninja), and Team 7's trainer/teacher. He wears a ninja mask covering his face up just below the eyes and wears his headband skewed on his head, covering his left eye. At first Naruto
, and Sasuke
think he's not much of a teacher nor ninja, but when Kakashi places them under his "Survival Training" course, the three "Genins" (rookie/first-level ninja) realize the value of teamwork in getting the mission done.
Kakashi's unique ability is the use of the Sharingan
in his left eye. yet Kakashi is not from Uchiha. The Sharingan allows the user to copy and predict the movements of any genjutsu or ninjutsu technique. He obtained it from a dying friend Obito Uchiha, who was dying in a failed mission, with half his body crushed, and gave Kakashi his eye after Kakashi himself had his left eye slashed out. During the timeskip, Kakashi is able to gain the Mangekyo Sharingan
, which allows him to create black holes, which was shown when he used it on Deidara
. However, he can only use it very infrequently, as it drains his chakra very easily to dangerously low levels.
He's worked and thrived at all levels, including among the ANBU. He has a summoning ability with a pack of Ninja Dogs, one of which speaks and all of which are excellent trackers. He's never been shown without his masks on. He wears at least two of them, and even his close friends don't know what he looks like. Even when bedridden and maskless in the hospital, blankets are strategically drawn to cover his face. But those who have seen him exclaimed he is quite handsome.
As a youth he was cold and efficient with little use for team members. His high success rate marked him as a great potential Ninja, and he looked down on those who were not. But that bad personality changed when one important mission went badly. He found himself in a cave which is about to collapse and a team member, Obito Uchiha, had half of his body crushed by a huge boulder. Kakashi was trying all his might to set Obito free. When it was obvious that Obito was not going to survive and that Kakashi and another team member, Rin, was likely to follow him, Obito decided and told his other team members to not rescue him and escape. Obito also wanted to give his Sharingan eye so they would help them escape from the enemies at hand. Rin, being a medical ninja, would remove Obito's Sharingan eye and she transplant it to Kakashi's injured left eye. Due to Obito's sacrifice, Kakashi learns the value of friendship and the importance of teamwork. And also, only in this way has anyone in the Naruto Universe gained the abilities of a 'Bloodline trait' without actually being a member of that particular bloodline. But as this is imperfect solution at best, he often tires after putting the borrowed eye into extended use. So much so he can be bedridden for days, or weeks.
When he learns of this he starts to cover it when not in battle as to help avoid the drain on his power. To Kakashi this event was a literal life changing experience. He became very dedicated to his future teams because it was a team mate's sacrifice that allowed him to live.