Taken from HealthyTextures.com....
Type 4
According to Andre Walker, if your hair falls into the Type 4 category, then it is kinky, or very tightly curled. Generally, Type 4 hair is very wiry, very tightly coiled and very fragile. Similar to Type 3 hair, Type 4 hair appears to be coarse, but it is actually quite fine, with lots and lots of these strands densely packed together. Type 4 hair that is healthy won't shine, but it will have sheen. It will be soft to the touch and will pass the strand test with ease. It will feel silkier than it will look shiny.
Type 4 hairs looks tough and durable, but looks can be deceiving. If you have Type 4 hair, you already know that it is the most fragile hair around. There are two subtypes of Type 4 hair: Type 4A, tightly coiled hair that, when stretched, has an S pattern, much like curly hair; and Type 4B, which has a Z pattern, less of a defined curl pattern (instead of curling or coiling, the hair bends in sharp angles like the letter Z). Type 4A tends to have more moisture than Type 4B, which will have a wiry texture
Type 3
When this type of hair is wet, it appears to be pretty straight. As it dries, the hair goes back to its curly state. When curly hair is wet it usually straightens out. As it dries, it absorbs the water and contracts to its curliest state. Humidity tends to make this type of curly hair even curlier, or even frizzier. Type 3 hair has a lot of body and is easily styled in its natural state, or it can be easily straightened with a blow-dryer into a smoother style. Healthy Type 3 hair is shiny, with soft, smooth curls and strong elasticity. The curls are well-defined and springy.
Andre defines two subtypes of curly hair. First, there is type 3A hair which is very loosely curled and usually very shiny with big curls. The shorter the hair is, the straighter it gets. The longer the hair is the more defined the curl. Then, there is type 3B hair which has a medium amount of curl to tight corkscrews. It's not unusual to see a mixture of these types existing on the same head. Curly hair usually consists of a combination of textures, with the crown being the curliest part. Lastly there is a type 3C, is hair type that is not in Andre Walker’s book, but many people suggest that it should be. This type of hair can be described as tight curls in corkscrews. The curls can be either kinky, or very tightly curled, with lots and lots of strands densely packed together.
Type 2
A relatively unusual type, wavy hair tends to be coarse, with a definite S pattern to it. There are three Type 2 subtypes: A- Fine /thin, B -medium-textured, and C - thick and coarse. Type 2A is very easy to handle, blowing out into a straighter style or taking on curlier looks with relative ease. Types 2B and 2C are a little more resistant to styling and have a tendency to frizz.
Type 1
Type 1 is straight hair.