The functionality will come via a patch, although will only be compatible with the new Xbox One S and of course, you'll need a TV which is compatible with HDR.
HDR offers a wider range of contrast and colour than standard TV's, which means that you'll see more details in your game. Only certain games support HDR at the moment, most of which are Microsoft first party games.
Sony fans aren't being left out though, as all PS4's will this week get HDR functionality via a system update. That'll mean that PS4 and PS4 Pro both support HDR, something that'll likely be patched in or built into most future games. It's already known that Battlefield 1 will support PS4 Pro, so it's likely that this HDR patch will also release for PS4 too.
Battlefield 1 arrives for Xbox One, PS4 and PC on October 21.