Race describes a character's physical features as a result of its species or heritage.
Published player character races and subraces include:
- tinker gnome[Dr422:9]
Mechanically, a.k.a. gamewise, your character's race is one of the most important things about them. Your character's race determines their physical dimensions and traits, such as height weight, musculature, and other aspects of their physical appearance. Your character's race does more than tell what they look like however, it also gives people a basic idea of what your character's personality is like. Many races (like Dragonborn or Goliaths) have certain characteristics drilled into them all their life, which means that they are almost guarenteed to act in a certain way, either because of a racial reputation that needs to be upheld, or a cultural responsibility. Often however, the "average" example of a race is only useful as a basic blueprint or starting point of a character. Remember, the most fun and memorable characters are usually unique in some way. For instance, the player's handbook 2 says that Dragonborn are best suited for heroic, leaderlike Thaneborn Barbarian builds, but in reality, they are just as well suited to the bloodthirsty Rageblood Barbarian builds, and since the average Dragonborn is an honorable warrior, a Dragonborn who is a savage brute is much harder to forget, and much more intetesting to play.
In the end though, personality and physical description aside, the most important aspects of a character's race are probably the things that are only mentioned while out of character. In other words, things like ability scores, size and speed, vision, language, skills, and special abilities. For instance, some feats are only accessible to certain races; While certain races get bonuses to different ability scores, which often makes them better suited for a certain class than other races. This doesn't mean, for example, that Eladrin Fighters are impossible, it just means they are much rarer than, say, Eladrin Wizards or Rogues, and that they probably have more difficult time adventuring than other characters who have picked a class better suited to their race. In the end, a character's race is one of the most defining aspects of a character, and often times one of the only differences between a Zero, and a Hero.
Race comparative table: https://spreadsheets.google.com/ccc?key=0AgQwMFOSmN5ldG5ROExVdElKRTk2aV9URFI4U3FBT1E&hl=en