1. Spun Threads
Throughout most of the 20th century, cotton thread was the standard sewing thread both industrially and at home. When synthetics were developed, it was only natural to attempt to emulate the sewing characteristics of cotton. 
Spun polyester thread, made from polyester fibers cut to the same length as cotton staple, was introduced as a substitute for cotton. All spun threads are made up from staple fibers that are spun into single yarns and then plied to make a sewing thread. 
Twisting together yarns made from short fibers, produces all spun threads. However, the staple lengths of the fibers utilized can have an important effect on the quality, strength, and performance of the thread produced. As a general rule of thumb, the longer the staple length of the fibers, the better the quality of thread produced. 
Spun threads have a more “fuzzy” surface which gives them a soft hand and good lubricity characteristics. They offer excellent sewing performance, but lack the strength of continuous filament threads.
2. Core Spun Threads
This process seeks to achieve the strength of continuous filament threads with the sewing performance of spun thread. Core spun thread features a continuous filament polyester core covered with cotton or polyester fibers. Two or more of these composite yarns are then twisted to form the thread. 
3. Continuous Filament Threads
This process begins by extruding individual filaments of synthetic material. A singling twist is applied to these unbroken, continuous fibers. They are then brought together and a finishing twist is applied. The result is a strong, consistent sewing thread. 
4. Textured Threads
This process adds texture to the parallel continuous filaments of synthetic yarns, creating softness and bulk. The textured filaments are then twisted slightly and heat set. These threads provide excellent coverage for seams and rolled edges. Textured threads are typically used in the loopers of a serger or over locker. 
5. Monofilament Thread
This is a single synthetic filament extruded to a specific diameter. They are available in a number of sizes, 0.12mm and 0.15mm being the most popular for the home sewer.