Charges

From WoWWiki

Items with charges are simply items that have limit on the number of times you can use them until it is dissapears.

For example [Discombobulator Ray] has only 5 charges, so it can be used only 5 times, after that it is gone (expended/destroyed/disappeared). The usual number of charges is 1 for explosives/bombs/enchants, and form 3 to 5 for various oils, poisons, etc.

These items usually could not be equipped but could be used directly upon your opponent or to enhance the items you are wearing/holding for some time or permanently (like the enchanting rewards from Zandalar Tribe).