What is a "guarantee" cabin?
Think of a booking a guarantee cabin like booking a hotel room - you don't book a specific room number at a hotel, but you might book an oceanview room or a suite. When you book a cruise, you do have an option to select a specific cabin number, but it's often more affordable to pick the cabin type instead and let the cruise line assign the exact cabin number. So if you pick a balcony guarantee, you'll have a cabin with a balcony and you'll find out the exact number by the time you board.