Theoretical framework of classifying market efficiency

It is widely assumed that “Asset Prices such as stock prices always incorporate the best information about fundamental values and that prices change only because of good, sensible information” (Shiller, 2003, page 83) Describe a theoretical framework of classifying market efficiency and assess to what extend the about quote is relevant in terms of explaining the pricing of securities on the financial markets. Additionally, assess to which extent and under which conditions such framework applies.