limits

well limits were pretty confusing to me, like there was certain things i still dont understand, for example: limit of int x as x ->3+. i dont understand the whole right and left hand limits. Also i dont understand when u have to identfy a limit as x->infinity or -infinity! lets see also a problem i couldnt figure out was: the limit of sin2x/x as x->0. well those were pretty much the main things i didnt understand!!