Theocracy is rule by God. In a theocratic government a human would act as liaison between God and the people. Usually this liaison would be a minister or priest of some kind. There have been many theocratic governments throughout history and currently such as Iran, Vatican City, and The Kingdom of Saudi Arabia.
Advantages of having a theocratic government would be control and unity. Controlling the people would be much easier because the leader would most likely say that any nonbeliever would be persecuted and probably die. And unity is a very broad word because it covers everything. The education would be unified under one solid set of things they were supposed to teach. There would be no debates over separation of church and state because the church and the state would be one. Unity over entertainment, no more debates over censorship because that stuff just wouldn’t be allowed. Everything would be unified under one man who talks to God. I didn’t say people would be happy, they would just be unified in their complete lack of individuality and strict standards that would be forced upon some of them.
Disadvantages would be the potential for abuse of power, lack of individuality, and unrest. Having one man do the entire rule making is pretty sketchy. He can say whatever he wants and no one will question him because he says that God said so. And with the probable conservative nature that God will be having the people take there will be a complete lack of individuality. Art will be censored, media will be censored, and generally everything will be censored. No more free expression that we as a people enjoy without a second thought. Also, if someone were to have the guts to stand up the man in charge and try to change things it could lead to unrest. Unrest never leads to anything good. Usually unrest leads to the overthrowing of the government or civil war which never ends well.