Recirculating skimmer mean that it have a skimmer pump that create bubble in the skimmer bubble by reusing the water in the skimmer body... And you will need a feeding pump to feed the skimmer with water from your tank...
Just my opinion, i dun really trust the rating for dymax equipment, they usually over-rate their equipments and if you are going for recirculating skimmer that you going to use for long term, i would recommend, Reef Octopus (Budget - $200 onwards), Hydro Performer (Budget - $500 onwards), Deltec (Budget - $800 onwards)....