Each character has several different attributes. All of the skills receive bonuses from each representative attribute. For example: the Melee skill gets a bonus from the Strength Attribute. Here is a list of all character Attributes.
Strength is a measure of how physically strong a character is. It controls the characters maximum carry weight, throwing range, melee damage bonuses, and throwing damage bonuses. Also lets the character wield heavier weapons without attack speed penalties.
Constitution is a measure of how sturdy a character is. Constitution influences hit points, stamina points, and resistances from poisons and illnesses. Determines the characters maximum healthpoints and stamina. Note that healthpoints are not gained at level up.
Agility is a measure of how agile a character is. It controls melee attack speed, bow attack speed, weapon swap speed, turning speed, and movement speed.
Intelligence is a measure of a character's problem-solving abilities. Intelligence controls the rate at which experience points are earned. This means smarter characters will be able to reach higher levels in much shorter periods of time.
Willpower is a measure of a character's common sense and/or spirituality. Wisdom controls a character's mana points, and a character's mental resistance against mind-altering magic. Legends say that Willpower can be used by Shamans to heal Permanent Injuries.
Willpower is Wisdom + characters level.
Charisma is a measure of a character's social skills, and their physical appearance. Charisma influences prices while trading, and unlocks certain characters.
Size is a measure of a character's size. Size influences hitpoints, movement speed, attack range, and melee damage bonuses.