A chain stitch sewing machine is designed to create a particular type of stitch known as a chain stitch. Unlike a standard straight stitch, which uses two threads (one for the upper and one for the lower), the chain stitch employs a single thread that passes through the fabric, forming a loop. This method results in a stitch that is both strong and flexible, making it ideal for various applications, including quilting, apparel manufacturing, and decorative sewing.