S/S=Summer & Spring , F/W=Fall & Winter, i.e., If you want boots keeping dog paws warm in cold weather,then Indoor-F/W-style could help. For some sporty activities, outdoor shoes would be a good choice,the rain boots keep pet's paw dry in moisture seasons and insulate or prevent bacteria.
Weight recommend: Outdoor boots- S fit breeds 8-15lbs,M for 18-25lbs, L for 30-80lbs, XL for 90-120 lbs.Indoor boots- S fit breeds under 5 lbs,M for 6-15lbs, L for 18-25lbs, XL for 30-50 lbs. Rain boots-S fit breeds under 1-7lbs,M for 8-15lbs, L for 18-25lbs, XL for 30-60lbs.