A rep works for the manufacture, the rep then educates the dealer, and ensures the dealers needs or questions are being taken care of. In most industries , the rep does get a commision and incentives... other wise how does the manufacture reward the best and hardest performing rep! The dealer is sometimes offered additional incentives via the rep.
In some industries a rep can sell a product without a dealer( typically to a family member).
Those manufactures that do not allow a rep to sell no matter what.. the rep will ofetn work out an "arrangement" with a local dealer, if there is a "special circumstance". In other words the dealer is going to get a sale they normally would not .. in turn the dealer sells it a reduced cost, making a bit of money for processing /handling the order.