The Ender Bag is an item that was added in the 8.08 Pirate Dungeon Update.
Since the Ender Bag is an equipable, it can be damaged. Bare this in mind when entering combat whilst having this item equipped, as it can break!
Previously, the player could right click the item to open up their Ender Chest without the need to place one.
However, this was changed in Update 9.0 with the introduction of Inventory Tabs. Players can now equip the Ender Bag to be given access to the Ender Chest Tab.