Intel Motherboards : (N3150TM-ITX): The 2-pin power header

I basically just signed up here, to ask a question that I could not seem to find a suitable answer for... So, here goes!

I have been toying around with the LUNA Design DNK-H ( http://luna-design.org/en/ ), and had originally intended to throw a Geekroo Fairywren+Raspberry Pi in there. Buuuut as it turns out, the DNK-H is quite serious when it says "Thin Mini ITX"... :I So, that kinda went against the wall.

However, in the process of that, I discovered a mysterious power supply cord on the base of the chasis: a two-pin plug. Within the packaging, I would find another one that could be soldered onto the board of my choice. Great!, so I thought, and had my dad solder that plug onto an ATX adapter. That, theoretically, should've worked. But as stated, the Fairywren based build didn't work due to sizes.

Now that this was out of the question, I wanted to pick up another mobo so I could occupy the DNK-H with something. One of the people at LUNA Design told me that for their "DNK-H Nano" configuration, they're using this thing: http://www.asrock.com/mb/intel/n3150tm-itx/

And look! Just behind the AC jack...there it is! Another one of these mysterious power ports.

Question:

What is that thing!

I have been trying to find other motherboards with a lower price tag with the same power header, but could not find any... Is this motherboard basically the only one having this, or what? x)

I do like the N3150TM-ITX, BUT I would like to not buy something expensive, when I can get a motherboard for a lower price tag.

Purpose of the build:

- NAT router (wlan <-> ethernet)

- File-/Printer server

- AirPlay/AirDisplay server

- OS: Linux (Goal: Debian 8)

Would be glad to hear back and have this mystery solved...

Thanks!