Hard to tell without knowing the weights. Off hand, 3,5 & 6 sound like machine embroidery thread, which you can use for quilting, especially wall hangings & table top items. 4 sounds like button hole twist, very strong thread, use to hem jeans. 2 is a brand name, not a thread type. Depends on the weight of the silk. you can quilt with it, also can be used for applique.