Warbound Until Equipped items are a new type that can’t be sold on the AH or traded, but can be taken by other characters for their use. Kind of like account-bound, except they become soulbound to that character once used. They should drop as personal loot at a slightly lower item level than other stuff, just to make it easier to gear up your alts without funneling power to your mains.
Its an account-wide bank! You shouldn’t have to mail anything to yourself anymore. There’s even a giant reagent tab, from which you can craft using any of your characters.