I wouldn't say there are 8 types as some of them actually intertwined. I'd say the most important types of sewing machines are regular sewing, quilting, embroidery, sergers, and coverstitch machines. Then, all of them can include some bells and whistles like some decorative stitches and again, all of them can be made for domestic use or industrial purposes. Some might be mechanical while others are computerized. In any case, you can read a complete buyers guide that goes over the different types here.