lol. It's a cyclone phase diagram based on the 18z GFS forecast of the low. It uses the modeled thermal wind and SR thickness symmetry to differentiate between cold and warm core and symmetric and asymmetric. Tropical systems are symmetric warm core, and extratropical cyclones are asymmetric cold core.
In this case, with rapid cyclogenesis occuring at the surface, the system develops a warm core as the surface low deepens quicker than the mid level low (thus the thickness between the two layers increases in the center of the storm). And the storm becomes vertically stacked, and sheds frontal boundarys, it becomes more symmetric, before dying. Pretty common evolution for this type of mid latitude ocean cyclogenesis.