Different types of items have different usages.

Equipment:

Click the equipment in the backpack can equip, appraise, repair, display or sell it.

Wear: Equip gears;

Appraisal: Appraise items;

Repair: Spend stones to add item's durability;

Display: Spend gold to display the stats of the item to all;

Sale: Sell equipment to NPC shop in return for stones;

Outfit:

Click outfits in the backpack can equip, display and sell them.

Pet:

Click pets in the backpack can equip, display and sell them.

Normal Items:

Click items in the backpack can use, display and sell them. Item will disappear from the backpack after use.

Quest Items:

Click quest items in the backpack can display and sell them.