A button hole sewing machine is a type of sewing machine that is used to sew buttonholes. Buttonholes are small pieces of fabric with two holes in them that are used to attach buttons to fabric. Buttonholes are typically sewn using a zigzag stitch, and a button hole sewing machine is designed to make this task easier. Some models of button hole sewing machines can also sew other types of stitches, as well as other types of decorative stitching.