Like any good RPG, there are a wide variety of items for the player to use. Each one has a purpose, even if simply selling for extra cash, and learning how to use each of them is key to succeeding
Item Effect
Book Access the Quests listing, Alignment

and Party Swap.

Potion Restores 650 HP.
High Potion Restores 2000 HP.
Ether Restores 650 RP.
High Ether Restores 2000 RP.
Elixir Restores 2500 HP/RP.
Phoenix Down Revives one ally with 20% HP.
Antidote Cures poison.
Dispel Herb Removes all aliments.
Sharp Stone Briefly increases party's P.ATK.
Barrier Stone Briefly increases party's P.DEF.
Resist Stone Briefly increases party's M.DEF.
Blink Stone Briefly increases party's EVA.
Seed of Life Increases Max HP by 50.
Seed of Mana Increases max RP by 50.
Seed of Strength Increases max Strength by 5.
Seed of Dextality Increases max Evasion by 5.
Seed of Agility Increases max Agility by 5.
Seed of Intelligence Increases max Intelligence by 5.
Soma Restores all party HP and RP.
Restoration Orb Revives fallen ally.
Power Drink Restores 20% of party SP.
Soul Drink Restores 50% of party SP.
Spirit Drink Restores 100% of party SP.
DS Teleport 3 Teleports party to guild.
Hollow Scripture Give to Toadofsky for information

on Ultra Bosses.

Holy Drop Fully restores party.