Final Fantasy XIV: A Realm Reborn is a remake/relaunch of Final Fantasy XIV. It is an MMO with similar mechanics, set in the Final Fantasy XIV universe, but it has been completely rebuilt from scratch. FFXIV: A Realm Reborn was announced for Playstation 4 as well as PlayStation 3 in addition to the previously announced PC version of the game at the Sony E3 2013 event.
The first question nearly everyone asks about this game is "How has it changed since the original version?" Well the answer is that nearly everything has been changed. Classes, Jobs, Locations and everything else has seen some work done. The questing structure was completely reworked and the game has basically evolved into an entirely new beast.
If you picked up the original and were let down, it is highly suggested you give the game a second chance. People who own the original version can simply download a large update for their version of the game to gain access to FFXIV: ARR. If you never played or purchased the original, you can pick up this new title as if it were an entirely new product, because really, it is 95% new.
In FFXIV, ARR features 5 Races. Each one brings its own unique style to the game and whatever the player chooses, their race will help mold what kind of character they grow to be. Most of the differences are cosmetic, but there is a slight stat difference depending on the race you choose and even the subset within the main race. The difference is tiny, so players should not feel like they will preform worse than others based on their choice.