There is no mana. Spells/skills require AP to use, and have a certain cooldown time.
Intelligence decreases the AP cost of skills (currently 1 AP less for every 2 Intelligence above the base value of 5). In the current build it also has an influence on how many ability points you get when you level, but the next update will remove that (within a couple days, or so).
There are skill requirements to learn certain spells/skills.
