An Item is an object which can be acquired by players. They may either be consumed immediately, be placed on the knight's belt, or be placed in the knight's arsenal.
These are items that are placed into the knight's arsenal.
Equipment can be wielded by a knight, providing advantages to offense and defense. Press the I key to access the arsenal.
Recipes are used to craft items through Alchemy Machines.
Upgrades are items that unlock premium features of Spiral Knights.
Consumables are items that can only be found inside Gates. Walking over them will cause a knight to immediately consume them, if they are capable of doing so. Examples include Crowns (currency), hearts (replenish health) and heat (consumables that upgrade your equipment after completing a dungeon).
Pickups are transient items, meaning that they will not be brought back to Haven with the knight. They are placed on the knight's belt, and can be utilized via quick access keys (default are the keys 1~5). Examples include Health Capsules and Vials.