Stat points are used to spend on stats and abilites (done by accessing the L menu), and are gained by levelling up.

Levelling Up - After you have gained a certain amount of experience you will "level up". When you level up, you gain 10 stat points.

Experience -To level up, you must gain a certain amount of experience. You get experience from damaging monsters, killing monsters, completing the map, and picking up experience shards dropped from dead monsters.