Combat in Final Fantasy III is turn-based. Each character and enemy takes turns acting based on their Agility stat. During your turn, you can select from various commands: Attack for physical damage, Magic to cast spells (requires MP and learned spells), Item to use consumables, and Defend to reduce incoming damage. Some jobs also have unique abilities, such as the Monk's 'Focus' or the Thief's 'Steal'.
Elemental weaknesses and resistances play a significant role. Pay attention to enemy types and adjust your magical attacks accordingly. For example, fire-based enemies are often weak to ice, and aquatic foes to lightning. Status effects can turn the tide of battle; 'Poison' deals damage over time, 'Blind' reduces accuracy, and 'Sleep' incapacitates an enemy. Always carry items like Antidotes and Eye Drops to cure these ailments. use your White Mage's healing spells to keep your party's HP up, and your Black Mage's offensive spells to exploit weaknesses.