They are fishtail braids, which means you take a section of the horse's main about 8-10 inches back from the bridal path and choose three thin sections to do one pass over of a normal braid. As you bring the next left braid section over, add just a little hair from the mane just next to where you are working, then bring the right side over and add just a little hair from the mane to the right of where you are working. With each time you weave the braid in, you keep adding little sections from the mane, until you have a "triangle" of mane woven into a three section braid that runs down the middle of the triangle.
With the show horse, they did at least two layers of these braids with two or three braids along the neck in each layer. At the end they split the "leftover" of the top layer and tied it into the ties of the layer below.
That's what it looks like to me, anyway.