Attributes are required to learn some skills, use some items, and affect the performance of your character. There are six core attributes. You start with a score of 5 in each of them and you can add 3 points every time you level up.
Strength (STR) allow you to wield more powerful melee weapons, deal more damage with them and utilize many hand-to-hand combat skill. Every point of strength adds 0.7 attack power to heavy one-handed melee weapons, 1.25 attack power to colossal weapons, 0.4 attack power to fist weapons and 0.4 attack power to light swords, 0.18 attack power to daggers and 0.3 attack power to bows.
Dexterity (DEX) allows the use of bows and other light weapons, increases their effectiveness, and improves your ability to dodge attacks. Every point of dexterity beyond 5 DEX adds 0.5% dodge chance (capped at 30% at 65 DEX, which can be further increased by passives and items), 0.5 attack power to light swords, 0.3 attack power to most one-handed weapons, 0.72 attack power to daggers, 0.4 attack power to fist weapons and 1.2 attack power to bows.
Intelligence (INT) is the primary stat of spellcasters, increases the power of magical skill and allows you to wield staves and other arcane tools. Every point of intelligence adds 1 spell power and 1.5 attack power to staffs.
Skill (SKL) increases the critical hit chance of all attacks, and is key to wielding many diverse spell and ability. Every point of skill adds 0.5% crit chance. Each point of skill adds 0.2 attack power to light swords.
Endurance (END) effects your maximum health and allows the use of heavy armor, as well as many abilities demanding a rugged constitution. Every point of endurance adds 5 HP and 0.3 attack power with Morningstar.
Charisma (CHA) improves the prices of items you buy and sell and is demanded by skills that require great leadership and willpower. Every point of charisma beyond 5 CHA reduces the cost of items by 1% and increases selling prices of items by 3.5%, capped at 45 CHA when the selling and buying price is equal. It also increases Radiance damage more than spell power. It also increases Holy Word healing power.
Pushing up on your core attributes in the character sheet will reveal additional information such as Crit %, Health, Attack Speed, etc. This information is very useful when determining the best gear to compliment your build.