Sharingan is one of the basic 3 dojutsus in the Shinobi World. Sharingan is a kekkei genkei known to be used by the Uchiha Clan, which is referred to as of an army. It is rather an interesting concept. The sharingan can only be activated by some worthy uchihas. This makes the doujutsu to be rare within the clan. By activating one's sharingan, the uchiha will gain one tomoe or pupil. This is great for keeping up with fast opponents and great for accuracy as well. The Sharingan can also see chakra flow within opponents and easily tell the difference between the original and a clone by glancing upon their chakra flow. Also the user can see their chakra if they are in a genjutsu.
There are 3 stages of the Sharingan; Sharingan, MS, and EMS (Rarely unlocked) The first stage grants the user 3 tomoes at max. At this state, the user will be able to copy jutsus and also percieve better aim/tracking speed. In the RP, it grants the same abilities although it is limited. The MS is the state of getting a 3t tomoe and experiencing the death of a close one. In RP and in NarutoVerse, the user will attain the 3 main abilities; susano'o, amaterasu, and Tsukiyoumi. However, there is a down side to such power. If overused, the eyes will die out, causing the user to be blind. This is where EMS comes. By using another sharingan eye and transplant it into the MS, the user will gain EMS. With this, the user can freely use the 3 main abilities without worrying of being blind.