In A Realm Reborn, Chocobos serve not only as a form of transportation, but also as a companion that will fight alongside you. Players will acquire their own Chocobo Mount at level 20+ through the Main Scenario Quests. At level 30+ players will unlock their Chocobo Companion that will fight alongside the player. Players can customize the looks of their players chocobo by equipping Chocobo Barding or changing their Colors. Players can further improve and personalize their chocobos through Chocobo Raising. In The Gold Saucer, players can partake in Chocobo Racing with special, race-bred birds.
To obtain your Company Chocobo, you must be level 20+ and have progressed through the main story enough that you have joined a Grand Company. To unlock the mount, you need to complete the quest My Little Chocobo. In the quest, you need to purchase a Chocobo Issuance from your Grand Company Quartermaster for 200 Company Seals. The game now gives you enough seals for the issuance directly from the Main Scenario.
Players can summon their mounts by dragging and activating the mount icon from Mounts Menu. You must first unlock the Company Chocobo before you can use any other mount you may already have (like from the Final Fantasy XIV Online Store).
Companions refers to the functionality that allows the Company Chocobo to fight alongside you. Players will not only be able to level up his or her Chocobo companion but also customize their looks and abilities. These aesthetic changes will be applied even while mounted. Players can specialize their personal Chocobos into tank, healer, or damage dealer by allocating their skill points into the Defender, Attacker or Healer skill trees.
To unlock the Companion, players must have completed the level 30 quest My Feisty Little Chocobo.
Chocobo Raising allows the player to train, improve and customize their Company Chocobo using a Chocobo Stable. This primarily is a passive means for Companion experience and a way to set their favorite food.
Chocobo Coloring allows the player to change the colors of their Company Chocobo while stabled.
Chocobo Bardings are customization items that can change the look of your chocobo. They do not give speed or stat bonuses.
Note that Chocobo Barding will change the looks of both your Mount/Companion Chocobo and your Racing Chocobo.
The map icon for Chocobo Porters is:“
Known for their masks modeled after the ever faithful chocobo, Chocobokeeps can be found at outposts across Eorzea offering adventurers use of their chocobo porter service.
Mounted on one of their specially bred chocobo, travel switfly and safely to one of several nearby stables. These chocobo have been trained to travel specific routes to their destinations, so relax, enjoy the view, and let these trustworthy taxis handle the rest.
Chocobo Racing is a Gold Saucer mini-game introduced in patch 2.51, allowing you to breed, train and race your own chocobo against other players in return for Manderville Gold Saucer Points and other rewards.
Note that your Racing Chocobo is NOT the same as your Mount/Companion Chocobo.
Despite the emergence of airships, chocobos have retained their place as a traveler's best friend. Be it as bearers of a merchant's wares, steeds for battle-bound soldiers, or an adventurer's means of locomotion; the long-legged avian creatures are still very much a common sight.
These flightless birds have sturdy legs with which to bear you across great distances swiftly.
The chocobo’s long tenure as the uncontested mount of choice among Eorzeans has allowed ample time for breeding, resulting in the wide variety of chocobos seen today.
The rouncey is Eorzea’s most popular breed. Rounceys are of middling size and extremely versatile, well suited to everything from pulling carriages to charging into battle. However, their willful temperament means they require extensive training before they can be handled.
Hulking chocobos bred for war, destriers can bear soldiers in full plate and withstand frontline clashes while leading a charge. Because their strength allows them to carry even heavy riders with ease, they are preferred by the bulky Roegadyn.
These diminutive chocobos were originally bred in Belah'dia for Lalafellin riders. Their small size is evidently the result of extensive crossbreeding with Near Eastern chocobos, and they are both gentle and obedient.
Palfrey, bred in Thanalan to thrive in arid climes, can travel great distances while consuming relatively little water. This has historically made them a popular choice for merchants and caravans traveling eastward. They are raised in great numbers in Ul’dah and Ala Mhigo today.
These Ishgardian chocobos are more often known as black chocobos, as their feathers' inky coloration is their most memorable trait. Given the proper training, any chocobo of the flyer breed can take to the skies.
The percheron is a rare example of a new tameable breed resulting from once-domesticated chocobos—Ishgardian ones, in this case—becoming feral and reproducing in the wild. At almost twice the size of the rouncey, a percheron can seat multiple riders; however, the breed’s volatile temperament means taming one well enough that it will do so is no small feat.
This peculiar stock is playfully referred to as “fat chocobos” among adventurers. They appear to be of a mixed breed, and unfailingly boast an insatiable appetite and a mass exceeding that of any destrier. 
The domestication of chocobos in Eorzea appears to date back to prehistory, with ancient paintings recently discovered near Ishgard showing tribesfolk using the flightless yellow cloudkin to till the earth, transport grain, and carry warriors into battle. While the overwhelming majority of chocobos seen in Eorzea today are of Coerthan stock, it is rumored that wild breeds of the species--including those which have retained the capacity for flight-still thrive throughout forests nestled in the vastly unexplored valleys of Abalathia's Spine. 
- Encyclopaedia Eorzea: Volume II, page 194
- Encyclopaedia Eorzea: Volume I, page 284