An inventory slot which can only contain equipment.
An inventory slot which can only accept certain types of item.
A slot which consumes fuel of some kind for smelting or other purposes.
An input slot used to supply items to a crafting, smelting, enchanting or other automated process.
A slot which contains the output of an automated process such as smelting, crafting, enchanting, etc.
A slot which belongs to a particular side of a "sided" inventory.