AP or Action Points are used by your units to perform actions, make attacks, apply buffs and use ordnance.
Whenever a Templar uses any number of AP, the same number of MP are also consumed. This strongly encourages move-then-fight tactics and slows down melee units more compared to ranged attackers.
Unlike MP, the number of Templar AP cannot be increased or decreased. It is always 5 at the beginning of the turn, unless the Templar is sufferent critical shutdown due to Overheating.