When creating a character, the first decision a player must make is that character's race. This will determine what region of the world your character will begin in, as well as their base starting statistics. The character's race is more than a mere cosmetic choice, as each race possesses various advantages and disadvantages which should be taken into consideration when deciding what kind of character you wish to make.
In addition to different starting stats, each race has access to 3 to 4 racial class masteries available at level 6, as well as a master class at level 55. Racial master classes are unique for each race, and typically have lower requirements to achieve than any other master class, but may offer little to no benefit to your character's base class. Never-the-less, racial master classes can sometimes be incredibly potent boosts to a character's abilities (ie; a Barbarian Rogue Berserker).
Note that while certain races may seem more tailored toward certain roles, this does not mean you have to be a particular race to excel as a particular class; for example, assuming identical gear, stat allocation, and class mastery choices, the differences between an Ogre Warrior and a Halfling Warrior would not be massive.