A variety of threads exists, in order to create differing textures.
Passing
passing is the most basic and common thread used in goldwork; it consists of a thin strip of metal wound around a core of cotton or silk. For gold thread this is typically yellow, or in older examples orange; for silver, white or gray. This is always attached by couching, either one or two threads at a time, and pulled through to the back to secure it. When multiple threads must be laid next to each other, a technique called bricking is used: the position of the couching stitches is offset between rows, producing an appearance similar to a brick wall. This same type of thread is used in making cloth of gold
Japan Thread
Japan thread, sometimes called jap, is a cheaper replacement for passing, and is far more commonly used in modern goldwork. It appears nearly identical, but rather than a strip of metal, a strip of foil paper is wrapped around the core.
Buillion or Purl
Buillion or Purl is structurally a very long spring, hollow at the core; it can be stretched apart slightly and couched between the wraps of wire, or cut into short lengths and applied like beads. This thread comes in both shiny and matte versions.
Jaceron or Pearl purl
Jaceron or Pearl purl is similar to buillion, but with a much wider piece of metal used in making it, such that it looks like a string of pearl-like beads when couched down between the wraps of metal. Lizerine is a very similar thread.
Freize or Check purl
Freize or Check purl is again similar, but the metal used is shaped differently, producing a faceted, sparkly look.
Faconnee or Crimped purl
Faconnee or Crimped purl is almost identical to buillion, but has been crimped at intervals.
Rococco
Rococco and the similar Crinkle cordonnet are made of wire tightly wrapped around a cotton core, with a wavy or kinked appearance.
Milliary wire
Milliary wire is a wire core wrapped with finer wire.
Plate
Plate is a strip of metal a few millimeters (1/8") wide; often this is used to fill small shapes by folding it back and forth, hiding the couching stitches under the folds.
Flat Worm or simply Oval thread
Flat Worm or simply Oval thread is a thin plate wrapped around a yarn core and flattened slightly. This is used like plate, but is considerably easier to work with.
Twists or Torsade Threads
Twists or Torsade, threads made of multiple strands of metal twisted together are also sometimes used, some of which, such as Soutache, sometimes have different colored metals or colored non-metal threads twisted together. These are either couched like passing, with the couching thread visible, or with the thread angled with the twist to make it invisible.