This falls under the unofficial category of “ask a simple question and get a complicated answer.” Sometimes the rate and room category for the hotel you select online will guarantee your bedding type (1 king bed, 2 double beds, etc.). When your bedding configuration is guaranteed, you will see the bedding and/or room type confirmed on your “My Trips” page and in your confirmation email.
If a bed type is not listed when booking your hotel and is not included in your “My Trips” and confirmation email, then you have a guaranteed room and rate – however, the specific bedding configuration will be assigned by the hotel upon check-in.
Hotels offer deeply discounted rates for “unspecified” bedding requests or “ROH” rooms. For these rates, the hotel will accept a bedding preference “on request,” but will not guarantee the room/bedding type until check-in.