Does the new 12" MacBook (2015) allow for dual displays, or just display mirroring? I have been unable to determine if the new 12" MacBook (the one with the USB-C port), when hooked up to an external monitor, will only mirror its retina display, or if it has the ability to use the external display for separate content.
You get two distinct, functioning displays unless you choose to mirror. Same with AirPlay.

From http://www.apple.com/macbook/specs/ :


  Dual display and video mirroring: Simultaneously supports full native resolution [2304 by 1440] on the built-in display and up to 3840 by 2160 pixels on an external display, both at millions of colors