Sharingan can Copy Ninjutsu, Taijutsu and Genjutsu techniques. But it copies the handseals and reads the flow of chakra (that is what handseals are for anyway) and then knows has said technique works. It's why they can't do any of the kkg/t/m techniques as they don't have the bloodline. Copying Rasengan is one thing, doing the actual technique is another story. Like with Sasuke learning chidori and not copying it and Lee's movement (he had to train to actually be able to do it, after copying it). Plus they need the actual affinity for the technique to do it. They can copy say like a earth technique but if the user doesn't have the affinity for the technique, he/she won't be able to do it.
