Paladins, Paladin Oaths, and Paladin Orders

When someone thinks of Paladins or Paladin Oaths they often times think of The Paladin Orders, of knights in shining armor who represent The Mantle's will in the world.
This is half true. Most Paladins are in fact divinely driven and religious, and they do usually use radiant energies to power their magical abilities. But that's not what really defines a Paladin. A "true" Paladin is simply one who has taken a Paladin Oath, an Oath that can be made to a multitude of things.
A Paladin Oath is a magically binding oath that the Paladin willingly enters into. The Oath itself is a set of agreements and ideals the Paladin agrees to uphold, and makes the Oath usually with the help of a Cleric or Wizard which helps bind them to their Oath. This allows them to draw on radiant and magical energies of the world on top of whatever martial abilities they may possess. But woe betide any Paladin who breaks this Oath, just as the Oath gives the Paladin their abilities it can also be broken and take away (or worse) the Paladin's abilities...
The vision of the divinely driven Paladin who serves The Mantle comes from the fact that most Paladins take the Oath of Devotion towards one or all of the Avatars and gods. But there are many other types of Oaths, with some popular ones being an Oath to the Crown, which dedicates a Paladin to a Nation or Monarch, the Oath of Vengeance, sworn by those wronged in some major way, or the Oath of the Ancients, sworn often by members of The Order of the Wind and Wood.
While Paladins can wander and follow their own way, most Paladins wind up in a Paladin Order. These Orders tend to be nationally independent Monastic Paladin Orders that worship a set of ideals or a particular avatar/god and maintain Order Halls across the continent. Some are large, having hundreds of members across the continent, some are small with only one hall in a local city. Some notable orders include The Order of Ascetic Enlightenment, The Order of the Dead Rose, and The Order of the Vengeful Cinders.
Paladins used to be relatively common in the First and Second Ages, but have gone down sharply after The Shifting in the early Third Age. This is a mixture of changing times, with holy knights being less "in vogue" than they were back then, as well as the effects of the Shifting causing more injuries/deaths from Paladin Oaths as well as having less magic users capable of administering the oath.