Chain stitch, be it in the wool, silk or cotton, is done by hook rather than by needle. The hook is referred to as ari, and quality for quality, hook work covers a much larger area than needle work in the same amount of time.
Crewel is basically similar to chain stitch. It is also chain stitch done on a white background, but here the motifs, mainly stylized flower, do not cover the entire surface, and the background is not embroidered upon. Wool is almost invariably used in crewel work and colourways are not as elaborate as in chain stitch. This fabric is available in bolts, and is sold by the length. They make excellent household furnishings being hand or machine washable