Here are some of the most important attributes:

Strength: Gives you a damage bonus for melee attacks and also increases the attack rating for certain weapons.

Dexterity: Gives you a bonus to your defense rating and increases the attack rating for certain weapons.

Constitution: Determines the amount of health and stamina your character has.

Intelligence: Determines the amount of mana your character has, and increases magic rating for mages.

Wisdom: Determines the amount of mana your character has, and increases the magic rating for priests.

Ratings and Resistances

These numbers basically affect your character's powers in attacking, defending, use of magic and more. They are altered by your attributes and possibly even what equipment you use.