This next picture is of the bridesmaid dress turned inside out. You can see the stitching line of how a sweetheart dip is sewn in the center front of the neckline.
Next all of the extra fabric is cut away and the seam allowance is clipped.
And here we have the final results. As you can see this gives the neckline a special touch.
The bride that wore this dress chose it because her ceremony was on a cruise ship. She didn't want a typical white wedding gown and adding a sweetheart neckline made the dress her own.