Items with charges (also known as "charged items") are simply items that have limit on the number of uses until they disappear.
For example, (tooltip shown on the left) has 5 charges, so it can be used only 5 times, and after that it is gone. The usual number of charges is 1 for explosives, bombs, and enchants, and 3 to 5 for various oils, poisons, etc.
Items with charges usually cannot be equipped but are used directly, either to act upon a target, or to enhance an item (like the enchanting rewards from the Zandalar Tribe).
Some buffs like Inner Fire also have charges, and the buff disappears when all charges are expended.