Wow you're online ay this hours? XD okay thanks btw!
I take it as sharingan in general so sharingan is a doujutsu, one of the great threes (byakugan, sharingan, rinnegan) Like all doujutsus it has the ability to locate chakra points in a person's body. Sharingan is unique because unlike byakugan and rinnegan, its skills in genjutsu are extremely high. Not only do they have the ability to perform strong genjutsus that would give the opponent a hard time of escaping, they also have an ability to spot genjutsu by checking if the chakra flow in their system is disturbed. There are levels of sharingans : 1T, 2T, 3T, Mangyekyou Sharingan, and EMS. Each sharingan levels gives the user enhanced abilities of the sharingan. For example, the MS could perform amaterasu but they will be recoiled with pain. However, EMS has the ability to perform amaterasu without the pain. Each level you upgrade your sharingan, you gain extra abilities like spotting higher level illusions..
Also, to awaken a sharingan the user will have to face a near death experience and has to grow hatred in their hearts.
Sasuke stares at his sensei.. scared at how he will be beaten up