This top has a deep open neck that dips into a half-circle. (A wider version of this is called a "scoop neck.")
A U-neck is good for triangles if the scoop rests far on your shoulders. This will make your shoulders appear wider—same as a square neck. A U-neckline can also be good for rectangles because it widens your shoulders, making your waist seem smaller. A shallow U-neck can draw the eye to the center of the body, which will make you appear slimmer. This is a good choice for full-figured ladies.