The BCS is a scientific framework for classifying drug substances based on their aqueous solubility and intestinal permeability. According to this framework drug products can be classified in 4 main categories:
Class 1: High Solubility – High Permeability
Class 2: Low Solubility – High Permeability Class
3: High Solubility – Low Permeability
Class 4: Low Solubility – Low Permeability
for further information you can download and see the attached guideline document for industry .