Consumables are single-use items that can be incredibly useful in battle. Potions heal HP, Ethers restore MP, and Phoenix Downs revive fallen allies. Status-curing items like Antidotes and Eye Drops are also essential. Always stock up on these before heading into a difficult battle.
Key Items are special items that advance the story, unlock new areas, or trigger specific events. These are usually obtained through story progression or specific side quests. Examples include the 'Zodiac Stone' fragments, 'Goug Machine City' items, and various letters or documents. Keep track of your key items, as they are vital for completing the game.