The principal message of the Basel II framework is Capital Adequacy. Basel II signaled a move away from a purely static regulator driven capital adequacy measure to an internal and relatively invasive assessment of the capital profile of a bank, called the Internal Capital Adequacy Assessment Process (ICAAP).Basel III introduces significant reforms to the Basel II framework primarily by setting out the supervisory framework for liquidity risk measurement via two minimum funding liquidity standards.

To understand Basel II & III, you have to start with the history of banking regulation. To put Basel II to work, you have to understand why the standard failed during the 2007-2009 financial crisis and why US regulators opposed it tooth and nail.