Could someone explain the different class of ships and why they are grouped that way. I am just a bit confused.

Thanks Chuckles

They are grouped that way because cruise lines usually order more than one ship of the same design. Thus, there are three Freedom-class ships but they are largely identical with minor decor differences, five Voyager-class ships with minor decor differences, etc.

Look here to see the various classes used by Royal Caribbean.

Chuckles,

it's actually even somewhat more complicated as RCI says on its web site:

The "Vision"-class is actually made up of three pairs of sister ships: "Splendour of the Seas" and "Legend of the Seas", "Vision of the Seas" and "Rhapsody of the Seas", and "Enchantment of the Seas" and "Grandeur of the Seas". Add to that that "Enchantment of the Seas" was lengthened some years ago, so she is also no longer a true sister to "Grandeur of the Seas", as well.

Also, there are quite a few differences between the first three "Voyager"-class vessels and the final two, as explainted on this very nice web site.