Inventory items

The Inventory Items can be acquired in this game by various means: they can be bought from shops (or merchant traders), they can be found in chests (or in skeletons) or dropped by some enemies. The order in which they are sorted in the Inventory is ??

They can be classified in four big categories:

Items
Here you can basically find Potions and Goos. These are items with a simple one use with a noticeable benefit. The benefit could be the recovery (partial or totally) of one of three statistics (HP: Health, MP: Mana or TP: Lust) or eliminating any negative status that a party character can suffer during combat.

See this page for more details.

Weapons
These are items that usually (there are already two characters that can wield them in the Off-Hand slot: Aka and Varia) can only be carried in the Weapon slot of the Equipment menu. In all but a handful of cases, they increase the Attack stat, the Magic Attack or both, but they also can increase other stats like Agility or Defense.

See this page for more details.

Armors
These are the rest of the equippable items. They are slot-specific: you can't put a Helm in the Accessory slot or a Headband in the Bodygear one. Usually they increase the Defense and or Magical, but all the other stats, visible or hidden (with the exception of the Luck one) can also be modified (not necessarily increased: in a good number of cases there is certain amount of trade-off).

See this page for more details.

Key Items
These are items related to the plot and don't require that you check them often. The exception is the Ledger, a portfolio given to you by Megail, that allows to check the investments that you had made already and the amount of PRoN available to spend.