|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, Sakura, 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. It is an ability unique to the Uchiha clan (Sasuke also has a weaker version of this ability), yet Kakashi is not from Uchiha. The "Sharingan" allows the user to copy and predict the movements of any genjutsu or ninjutsu technique used against him (except for bloodline trait techniques). Of course, you would have to SEE the ability/technique first in order to copy it. Since Kakashi is not of the Uchiha clan, using the Sharingan strains his body.
The story of how Kakashi obtained his Sharingan comes from the manga, told in Kakashi Gaiden, which is the side story that separates the two parts of Naruto. After Kakashi Gaiden, the Naruto story picks up again 2 1/2 years later. Currently, the anime series is still in the first part of the Naruto story and hasn't yet reached the Kakashi Gaiden part. However, odds are that Kakashi's Sharingan origin will be the same (or at least very similar to) the one in the manga. Anyway, lets get on with it....
When Kakashi graduated as a jounin, his teammates had to give him a present, but Uchiha Obito forgot. They also had to do a mission on the same day. On that mission to the grasslands, they got attacked by a group on rock ninjas. The rock ninja's can turn invisible, and slashed Kakashi's left eye (that's how he got the scar). Later, Uchiha Obito gets his whole right side crushed by a huge rock thrown by a rock-ninja. With the last of his strength, Obito tells Kakashi to take his left eye as he will no longer need it. So then Rin, with her special ability, transplanted Obito's eye to Kakashi. During the timeskip later in the series, Kakashi develops his Sharingan into the Mangekyo Sharingan, which is basically just an enhanced version.
Kakashi is not without his "lighter side", though, as one of his "quirks" is reading some kind of adult books titled "Icha Icha Paradise" and "Icha Icha Violence". Nothing, not even survival training, can stop Kakashi from reading through the pages just to "see what happens next"!
Oh, and the reason Kakashi is always late is because his best friend, Obito, was always late, and he choose to adopt his old friend's habit. Unfortunately, Uchiha Obito's body was never recovered, so instead of a grave, he visits a large stone monument that serves as a memorial for all those who died for the mission's completion.
Kakashi's name literally means "scarecrow".