Rabbi, Dayan, Posek-

A Rabbi, is someone who went through the long process if Smicha-No, it does not mean blanket, but the meaning here means "Covered".The basic knowledge of a Rabbi is: Shulhan Aruch- Orach Haim, Yoreh D'eah, and Coshen Mishpat. Most Yeshivot, only let people get Smicha if they have a long Yeshivah experience.One must get Samuch by a Posek, and approved by a Beit din. The usuall Smicha programs are, about 3-7 years. The next level is Dayan-A judge, this is very hard one must have mastered the entire Choshen Mishpat, of Shulhan Aruch, with every commentary, opinion, and side. The highest level, of a Rabanut is Posek. A Posek may, change a law the was not in the Torah(Written, and Oral). This Posek, must know pretty much everything about Judaism.