Not sure about the sizes above. These are a Medium, which will suit a child of about 10 - 20 lbs, so 6-8 weeks up to about a year old. They are "white" but I'd say they're really off-white. They are in good condition - the elastic and velcro are fine, and there are no stains.
They are wraps. They are waterproof and are designed to go over the (absorbent) bit of the nappy itself. We used them very successfully with flat terries, which suited us as they are easy to dry (and cheap to buy!) However, they will also work with many of the shaped nappies which don't have their own waterproof layer.
Six wraps should be all you will need as you don't need to change the wrap every time you change the nappy. You can use the same wrap all day (unless it gets soiled, of course) then one at night. We found that the gussetted bit of the leg was a great design and good at containing anything which might manage to escape from the nappy itself. (I know, too much information...)
Washable at 60C.
Non-smoking home. Been washed with biological powder.