After choosing your character’s species, you select their character class. A character class is like a profession or career. It is what your character has worked and trained at during his younger years. If you wanted to become a doctor, you could not walk out the door and begin work immediately. First you would have to get some training.
The same is true of character classes in the game. Your character is assumed to have some previous training and guidance before beginning his adventuring career. Now, armed with a little knowledge, your character is ready to make his name and fortune.
The character classes are divided into four groups according to general occupations: mage, priest, rogue, and warrior. Within each group are several classes. All classes within a group share the same Hit Dice, as well as combat and ability proficiency. Each class within a group has different special powers and abilities that are available only to that class. Each player must select a group for his character, then a specific class within that group.