Type 1s are straight, type 2s are wavy, type 3s are curly, and type 4s are coily. The sub-division of A to C depends on the diameter, width, pattern of your curls and the shape they curl into. Type As have a wider pattern size, type Bs medium, and type Cs the smallest of the three.
Each type requires a different hair care routine, that is why it is important to identify it. You may think you have wavy porous hair your whole life, until you try to change your hair care routine and discover that it has always been curly.