These are not necessarily the names by which such characters refer to themselves, of course. A Psychic might call herself a mystic, witch or medium. An Adventurer might call herself a ranger, scout, burglar, spy or simply an expert. A Warrior might call himself a soldier, martial artist, mercenary or simply a fighter. Each class has a core rules (the Base Attack Bonus, Hit Die, Bonus Feat progression and - for Psychics - Psychic Powers).
Abbreviated to BCB, this number is added to all attack rolls. Additionally, as a hero (that is, any one with a heroic class level - whether they're heroic or villainous), you gain a heroic bonus to Defence equal to your Base Combat Bonus.
This is the type of die you roll to determine your Vitality Points. You will have the maximum number of Vitality points at 1st level. After that, you roll the die each time you gain a level. (Some GMs allow you to choose the “high average” of a die (half the die number, plus one) instead of rolling - check with your GM.)
Each class has one or two good saves and one or two poor saves. Your character choice designates which saves are good or poor. If the character later gains a level in a different class (see Multiclassing, below), that designates which saves are good or poor for levels gained in that class.
Each class has a specific number of class skills, as given in the class description.
Aside from skills, fighting and - for Psychics - psionics, each role has feats that they excel at. The class description lays out the feats you gain as you advance in experience within a class throughout the character's career.
Some feats have prerequisites, which you must meet in order to qualify for the feat. Make sure you spend enough skill points, and have at least the minimum ability scores to meet these prerequisites.
When you gain a new level, instead of gaining the abilities granted by the next level in your character's current class, he can instead gain the 1st-level abilities of a new class, adding all of those abilities to his existing ones. This is known as “multiclassing.” There are a few special rules to take into account when you take a new class.
Background: You do not gain a new background.
Class skills: You only gain new class skills if the number of class skills your new class has is more than your old - and only as many as the difference between the two.
Character level: Note that there are a number of effects and prerequisites that rely on a character's level or Hit Dice. Such effects are always based on the total number of levels or Hit Dice a character possesses, not just those from one class.
Example: For example, let's say a 5th-level warrior decides to dabble in the psychic arts, and adds one level of psychic when he advances to 6th level. Such a character would have the powers and abilities of both a 5th-level warrior and a 1st-level psychic, but would still be considered a 6th-level character. (His class levels would be 5th and 1st, but his total character level is 6th.) He keeps all of his feats gained from 5 levels of warrior, but can now also manifest up to Tier 1 effects. He adds all of the hit points, base attack bonuses, and saving throw bonuses from a 1st-level psychic on top of those gained from being a 5th-level warrior.
Each character begins play with a single favoured class of his choosing —typically, this is the same class as the one he chooses at 1st level. Whenever a character gains a level in his favoured class, he receives either + 1 Vitality point or + 1 skill rank. The choice of favoured class cannot be changed once the character is created, and the choice of gaining a hit point or a skill rank each time a character gains a level (including his first level) cannot be changed once made for a particular level.