it's actually a pretty killer feature that Nvidia had promised 3 years or so back before apparently getting sidetracked on the video acceleration stuff.
what this means is that gnome/xrandr/etc will no longer see all your monitors as one big virtual display, but as independent ones that can be controlled/arranged/resized/etc via gnome/xrandr/etc. you can now script monitor attach/detach (or make use of gnome-managed auto-detection) to dock/undock events, or hotkey bindings. In the past you had to resort to twiddling around in nvidia-settings to do it, which is a major pain for laptops with docks, or for people who switch on/off output to their TVs regularly.
it also means window managers that are "display aware" and do things like allow you to independently control/switch workspaces on a per-display basis will actually work with nvidia proprietary drivers now that they are no longer "tricked" into thinking you just have one big display.
in general it means that display configuration for nvidia cards is now, finally, up-to-par and identical to intel/ati/nouveau/etc, which, via xrandr, had long since surpassed nvidia-settings for this task.
previously nvidia only supported xrandr 1.1 or so, which was basically just resize/rotate: neither of which worked right for multi-monitor setups due only a single virtual display being exposed. (it was doable via nvidia-settings, but not scriptable, and not interoperable with common management tools used for other cards)
it's really great stuff, and it has taken nvidia off my blacklist for linux workstations cards. really glad to see the nvidia folks hadn't forgotten about this.