Briefly, it's a polo neck sweater without the sweater bit. In other words it's just the polo neck and a bit to 'tuck in' and is really useful to use instead of a scarf as a snug neck warmer.
The pattern was a free download with my Burda Magazine and I ended up making one in Navy with a wide rib and a plain white one made out of a T-shirt fabric remnant.
They were both so quick and easy on the overlocker just joining the two side seams and overlocking the edges. It also used up some small remnants so quite a win really.
You can get the free PDF download pattern from here. This is what it looks like after you've downloaded it and stuck it together. I've also shown the page from the February 2016 Burda Style Magazine showing the latest trends and how to make it.
I have to admit that I adapted the Navy version as the ribbing was too lax and didn't spring back into shape once it had been pulled over my head. I made a ring of wide, soft elastic and secured it to the insides of the dickie at the point I wanted the fold. The result is a more comfortable and stable polo that doesn't droop down. This wasn't needed in the white version as the T-shirt fabric was firmer.