The inventory window is a section where your character stores your items and gold that you have collected throughout the game. Your gold is located on the bottom right hand corner of the window. In the bottom left hand corner of the window is the equipment dismantling hammer, which lets you dismantle your equips into souls.
All items are split into 4 categories which can be selected by clicking on their tab.
All your weapons, amours and souls are stored in this section.
All stat effecting potions, food, recipes, seal removal scrolls and refining powders are stored in this section.
Random items dropped by monsters are stored in this section which includes ingredients for recipes.
All items purchased from the Cash Shop and items gained from gift boxes are stored in this section.