Sometimes referred to as the embroidery foot, the darning foot is used for "free hand" embroidery and darning to ensure proper stitch formation, minimize skipped stitches and puckering and also protect your fingers while you move your fabric freely under the needle.
Especially beneficial to those just learning how to do free hand embroidery. The open toe version greatly improves visibility of stitches and is especially popular with quilters.
Low Shank fits most 7mm machines