Exception: Carnival has several cabins which are classified as inside cabins but actually have a french glass door which allows light into the room (no balcony, but the door can be opened). Carnival also has some cabins that have a window, but because the window has an obstructed view (that means there is a railing or object in the way) it is listed as an inside cabin. Royal Caribbean has some cabins that have a window but look out over an inside promenade area. These are called "promenade staterooms".
All cabins come with basic amenities, such as the services of a cabin steward to clean your room and turn down the beds, soap and shampoo in the bathroom, individual climate control, etc. But certain categories of stateroom come with added perks. Suites come with a variety of extras and privileges, everything from priority boarding to in-cabin bar setups. Spa cabins will offer spa-related perks, such as yoga mats in the cabin or a fancy showerhead; concierge-level cabins will give you access to a concierge and niceties like afternoon canapes; and even solo cabins might offer extras, such as the use of an exclusive lounge. How do you want to be pampered on your vacation?
Some cruise travelers prefer their cabins to be near to (or far away from) specific areas of the ship. Sun-worshippers might prefer an upper-deck location close to the pools and sun decks, while partiers might want easy access to midship entertainment hubs. Travelers with mobility concerns may prefer a stateroom close to a bank of elevators.
Your room on a cruise ship is called a cabin (or stateroom) and is akin to a hotel room, but typically much smaller. Choosing a cruise ship cabin can be fun and challenging at the same time, and not just a little bit frustrating on occasion. You need to discover the cruise deck plan first. Cabins fall into different types or "categories," and some cruise lines will present as many as 20 or more categories per ship. Before you get overwhelmed, it is helpful to remember that there are essentially only four types of cabins on any cruise vessel.