narutos logic is stupid and and un thought through the tracker ninja only "killed" him after kakashi and him close to dead and it was a surprise attack i really dont know what the point of that scene was.
a quick full explaniton of the Sharingan: in general it gives the owner 3 primary abilitys 1st is extreme high speed visual tracking of targets to near precog speed, 2nd is the ability to easly cast genjutsu, 3rd abiity to see chakra