Ship rating is the reflect price levels and facilities, could be interpreted as:
Budget - Older ships providing Value for money cruises
Standard - Older ships providing good food and service, or fairly new ships with a wide range of facilities
Superior - Mostly new ships serving the mass market, with fair sized accommodation, adn good food, service and entertainment
Premier - High class ships with more space and better service
Luxury - Excellent cuisine and personal service in spacious elegant surroundings