To figure out your hair's texture, grab sections of it on the top, sides and back and watch how it falls when you let go. If your hair falls flat and limp, you have fine hair. If your hair sticks up straight or if it poufs up and away from your scalp and face, you have thick textured hair. Anything in between is medium texture.
Naturally blonde hair tends to be thinner in texture, while dark hair tends to be thicker.