Item

An Item is any object in the game that can be placed into your inventory:
 * Weapons
 * Focus Items
 * Pieces of Armor
 * Quest Items
 * Crafting Materials
 * Collector Items
 * Unique Items
 * Runes
 * Vials of Dye
 * Identification Kit
 * Superior Identification Kit
 * Salvage Kit
 * Expert Salvage Kit
 * Superior Salvage Kit
 * salvaged Weapon Upgrades

Note that some people exclusively mean Focus Item when they say "Item".