All-purpose thread is 100% polyester and is mostly used with light to medium weight fabrics and needles. All-purpose thread can be used for many projects like apparel, drapery, and crafts. Upholstery thread is 100% nylon and can be used for outdoor and heavyweight upholstery fabrics. It is stronger and thicker than all-purpose thread, and is also weather resistant. Both threads can be used for machine and hand sewing.