, means only the stay is included in the rates and you will have to pay extra for using the dining facilities at the hotel. In general terms, it can be called the "Room Only" Plan.
, is where the hotel includes a daily breakfast with your rooms stay. The hotel can either affix a breakfast menu of its choice or provision for a buffet breakfast in the dining area. Again, whether the breakfast is served by the room service or in a common dining area, depends on hotel to hotel.
, includes all three meals, breakfast, lunch and dinner for the length of your stay. Generally the rates on this plan are higher but offer a good value for your money, and of course added convenience.
, is a slightly altered version of the American Plan, and includes a room stay with breakfast and a choice between lunch and dinner. Some hotels may have a fixed lunch or dinner policy where you cannot switch between the two, but generally it is for the convenience and cost benefit of those guests who are expected to be away (for work etc.) during noon or evening hours.