There are many threads on the market today developed for different purposes, here are the three most common types.
All-purpose sewing threads is made of synthetic, cotton or cotton covered polyester. This type of thread is used for sewing garments and projects.
Embroidery thread is made of various fibers; rayon, polyester, acrylic or metallic. These threads create a smooth glossy appearance for embroidery and other decorative stitching.
When embroidering, use embroidery bobbin thread because it is fine weight and will not build up under embroidery
Note: When using a metallic or a flat film thread for embroidering, you may need to use a needle with a larger eye and lower the embroidery speed. Thread the sewing machine with the spool in the vertical position.
Transparent thread, also called monofilament thread, is single clear synthetic thread. It is used for quilting and other decorative sewing. Thread the sewing machine with the spool in the vertical position.
When winding a bobbin, wind at slow speed and wind the bobbin half full.
Note: Some fabrics have excess dye which can cause discoloration on other fabrics or on your sewing machine. This discoloration may be very difficult or impossible to remove.
Fleece and denim fabric, especially red and blue, often contain excess dye.
If you suspect that your fabric/ready-to-wear garment contains a lot of excess dye, always pre-wash it before sewing/embroidering to prevent discoloration of your machine.