An inside cabin, is just that, a cabin on the interior of the ship with no windows outside. While some lines may have very small inside cabins, Celebrity has generously sized inside cabins that are the same size as ocean view or balcony rooms.
Ocean View cabins come with....you guessed it, a view of the ocean! This simply means you have a window to the outside of the ship. These rooms are the same size as balcony rooms, just minus the balcony.
You will always hear Celebrity refer to "balcony" cabins as "verandahs." These cabins come with a balcony that will have two chairs and a table.
On Millennium Class ships Concierge Class cabins are slightly larger than Verandah cabins. On Solstice Class ships they are the same size as Verandah cabins. On both ships this class of cabin comes with some extras such as foot stools on the balcony, priority check-in, embarkation lunch, etc.
Aqua Class cabins are the same size as the Concierge or Verandah cabins, however they have improved showers, great placement on the ship, and the ability to access both Blu for breakfast / dinner and the relaxation room & Persian gardens.
Suites vary in size from Sky Suites up to Royal and Penthouse suites. Each suite on Celebrity has a butler along with access to Luminae the Suites only restaurant plus Michaels Club access along with many other perks.