When an item is ‘Bound to Account’ it can be transferred via mail to any character on your account, as long as the character are on the same shard. A ‘Bound to Account’ item is not shared on every character and items which are consumable or collectible, such Mounts or Companions, cannot be sent to other characters once used/consumed. Please use caution prior to consuming or collecting a ‘Bound to Account’ item.