Braid' generally refers to a woven, long piece of narrow fabric. Flat cross-section braids were often used for belts, straps or trim for edging clothing. Circular or square cross-section braids were often used for draw-strings, poynts etc. Very narrow, elliptical or flat-on-one-side braids were used in couching (see below).
The braid could be made seperately and stitched on later, or be made as the clothing is being made (ie made as part of the clothing). It could be laid down straight, or following seams in the clothing (even concealing them), or laid in decorative loops/patterns (known generally as couching). Some braids were also used to add strength to edges, for example, to stengthen the seam along the edge full of buttonholes - to prevent the buttons tearing the fabric.
Braids can be made in a variety of ways, most common (in the SCA) being: