Aft is the back, (also called the Stern) and Bow is front. Port is the left side (remember by knowing that "port" has the same number of letter as "left" and Starboard is the right side.
On the cruise ships, the Aft balcony cabins have bigger baconies (because of the shape of the back end of the vessel) That's why the people like them. Also, a normal balcony can be very windy, while the Aft balconies are not because the ship blocks the wind.
Carnival Cruise Lines:
Fantasy 90, Celebration 95, Victory 05, Conquest 05, Spirit 6/06, Freedom 6/08, Holiday 7/08, Victory 6/09, Valor 9/09, Dream 6/10, Splendor 8/10,Conquest 8/11,Magic 11/11,Triumph 4/12,Spirit 7/12,Freedom 11/12, Triumph 2/13 - The fire cruise, Magic 1/14
NCL Dream October 2006, RCCL Mariner OTS June 2007, Celebrity Silhouette 2013