Warmbloods in general are more of a type in and of themselves rather then a specific breed. There are several 'breeds' that the hobbyist is undoubtedly familiar with, among these the Trakhener, the Hanoverian, the Selle Francais, and the Holstein. Several countries are trying to develop their own breeds, notably the Dutch Warmblood, the Swedish, the British, and North American, and Australian Warmbloods. Of these only the Trakhener can almost be considered a pure breed; the others depend or depended heavily on native stock crossed with Trakheners (originally the only major type available).
The area of present-day Germany is the heart of Warmblood breeding. There are five major breeding districts; the names of which are applied to the horses produced there. These are (alphabetically) Baden-Wurttemburg, Bavaria, Berlin-Brandenburg, Hannover, Hessen, Holstein, Oldenburg, Rheinland, Rheinland-Pfalz-Saarm Sachsen, and Westphalia. There are a few others but they are rather obscure. Trakheners are bred throughout the country. Each type has its own unique brand, which makes it easy to identify the geographic area the horse originated from, if you can remember exactly what that brand stands for!
So what is a Warmblood? The name rather implies that it is a horse midway between the hot-bloods (Arab, Thoroughbred) and the cold-bloods (Drafters). According to Jane Kidd, the terms appear to derive from the German Kaltblut, meaning phlegmatic (though the literal translation is cold blood), and Warmblut meaning a manageable temperament (Clarke and Wallin 1991). These terms importantly do not refer to blood-mixes but temperament. For the most part, the Trakehner, Hanoverian, and Holstein have seen the most extensive use in creating the newer Warmblood types.
Probably the single most important aspect of the Warmblood as a type is that the individuals are not of any fixed breed type, but rather a harmonious blend to create a specific type of horse suited for sport and driving events. This means that horses outside an area were used heavily for development of a type in each of the different areas. A pedigree student will often find the initials OX or XX or even X in Warmblood pedigrees. These denote outcrosses to other purebred mares and stallions of Arabian or Thoroughbred stock which were inspected, approved, and registered in to the breed stud books. Any horse with OX after its name means it is a pure-bred Arabian graded into the stud books. Thoroughbreds graded into a stud book are designated by XX. An Anglo-Arabian graded into a stud book is denoted by X (capital). Finally, an x (lower case) is used to show a cross-bred individual. These essentially "not Warmblood" horses were introduced to add refinement, size, and other qualities deemed necessary by the breeders. Several Arab and Thoroughbred sires are listed as foundation sires in Trakhener and Hanoverian stud books.
As for other abbreviations, the most common one I've come across while researching Warmbloods is the "v," the "von," or the "V." All of these stand for the German word von, meaning by or from. So, in pedigree terms, if you saw the name Butow v. Mahogani or Butow von Mahogani, that would imply that horse is by Mahogani. This is more frequently used in naming a dam's sire, however; the Mahogani name is only an example.
So what else can be of help to the pedigree assigner? Well, one very important regrettably overlooked part of PA is the naming process for Warmbloods. With one exception, the Trakehner, all warmbloods are named with one or two word names that start with the same letter as the sire's name. This handy practice makes it rather easy to track pedigrees since there are a limited number of family names. All Trakhener names start with the first letter of the dam's name. I've heard this is in deference to the memory of the mares that survived the flight from East Prussia (now in Russia) to Germany to escape the ravages of war during World War II. This 900 mile trek was responsible for near decimation of the breed as only a handful of mares survived. Hence the naming strategies are reversed for Trakehners to honor those mares. In general the North American breeders aren't so hung up on this tradition. I've seen quite a few horses out there with names not entirely appropriate if we're going for realism. In most cases I'm sure the owner just liked the name for the horse, and I have no problem with that. Most of my Warmbloods are named in the traditional manner, and those that are not are getting their pedigrees revamped to accurately reflect what I want in my program. Of course, it's always best for you to do whatever makes you happy, regardless of what "tradition" says!