In Naruto who is obito?

Answer 1

A childhood rival of Kakashi. They originaly hated one another, but that changed when they went on one fateful mission... (Text taken from Narutopedia)

They had been sent to spy on enemy forces during the third ninja war:

Rin (their female teamate) was kidnapped by two Iwagakure ninja named Kakkō and Taiseki. Obito immediately suggested that they rescue her, but Kakashi disagreed on the basis that they needed to complete their mission, opting not to make the same mistake his father did. Obito would not hear of it and stubbornly left to save Rin, but not before mentioning that he believed Kakashi's father, the White Fang, was a true hero. Shortly after parting ways, Kakashi reflected on Obito's words and Rin's prior kindness. He realized that his father was not wrong after all, which prompted him to join Obito in the rescue effort.

Once they made it to where Rin was located, Taiseki was able to attack and damage Kakashi's left eye, who took the blow that was intended for Obito, giving him a permanent scar. In sheer terror and desire to protect Kakashi, Obito finally awakened his Sharingan, allowing him to see through his opponent's camouflage jutsu, kill the attacker, and continue on to Rin. Once they located Rin and Kakkō, Kakashi and Obito teamed up to defeat the latter. Kakashi and Obito freed Rin, but just as Kakashi's team was about to leave, Kakkō attempted to trap them with a crushing technique, causing a cave-in.

While trying to escape, Obito pushed Kakashi out of the path of a falling boulder, causing himself to be crushed beneath it instead. Knowing his life was at an end, Obito instructed Rin to implant his left Sharingan into Kakashi's damaged eye. Rin complied, and as soon as the surgery was completed Kakashi used the Sharingan and his Chidori to kill Kakkō.

Obito's death had a huge impact on Kakashi's personality. He is now more cheerful and shows greater concern for his team-mates and students, placing their safety over the successful completion of a mission, as well as believing that teamwork is essential to overall success as a team. He is also regularly late for appointments, making obvious excuses just like Obito before him. This is because of his frequent visits to the memorial where Obito's name is engraved, where he loses track of time.

Answer 2

Obito was kakashies rival and friend back in the ninja accademy and he was crushed. He gave kakashi his remaining sharingan