Curls are more looser and elongated, the texture and feel is more on the finer I like to say silkier side.
This is just about the same as 3a but a bit more thicker but the texture is still on the finer and silkier side.
Getting to the more thicker, bigger more coily than those in 2a-3b. Texture runs about the same but some in this hair type may experience more dryness and coarseness than those in 2a-3b.
This is the type that I myself am in, and speaking for myself I am what you call multi-textured. Some parts of my head are different from others. This type is more on the kinky, coily side of natural hair and this type is the most driest. Type 4's need a bit more moisture than the other types and type 4 experiences breakages as well as shrinkage's more often than those in other types.
Bonus Texture is the multitexture any one of the types can have multi-texture type hair whether you are in the 3s or 4s or 2s. Natural hair grows how it wants and does what it wants. The point of this chart is to just give the basic idea of curl types and patterns and some charts even offer suggested products. Although I would like to point out the issues of hair typing and the chart that is another post for another day. I just wanted to simply explain quickly different types of natural hair. I hope you enjoyed this quick little post. =)