Simply stated, the seller will pay a different commission if the property is sold by the listing broker.  The listing agent must disclose this when entering the listing into the MLS by selecting Y on item (49) VAR RATE Y/N.  Please see the rule below for the full explanation as stated in the Tahoe Sierra Multiple Listing Service Rules and Regulations.

7.22 Dual or Variable Rate Commission Arrangements. The existence of a dual or variable commission arrangement shall be disclosed by the listing broker by a key, code or symbol as required by the MLS. A dual or variable rate commission arrangement is one in which the seller or owner agrees to pay a specified commission if the property is sold by the listing broker without assistance and a different commission if the sale results through the efforts of a cooperating broker, or one in which the seller or owner agrees to pay a specified commission if the property is sold by the listing broker either with or without the assistance of a cooperating broker and a different commission if the sale results through the efforts of a seller or owner. The listing broker shall, in response to inquiries from potential cooperating brokers, disclose the differential that would result in either a cooperative transaction or, alternatively, in a sale that results through the efforts of the seller or owner.  If the cooperating broker is representing a buyer or tenant, the cooperating broker must then disclose such information to his or her client before the client makes an offer to purchase or lease.