Artist brushes are made of four parts: hair/bristles, ferrule, crimp, and handle. Bristles are the hair. The handle is a holder made of wood or acrylic. The ferrule is the metal bit that connects hair to the handle. Crimp fastens the ferrule to the handle.
Artist brushes come in long and short handles; they also can be made of natural or synthetic hairs (sometimes a combination of the two). Longer handles allow for more gestural work and shorter handles are more suited to detail work. Natural hair brushes are most commonly made using ox, hog, sable, and squirrel hair. Acrylic and oil brushes tend to have longer handles and require stiff coarse hair (usually hog hair) to spread thick layers of paint. Watercolour brushes tend to have shorter handles and require fine hair (usually sable and squirrel) for holding liquid and doing washes. Synthetic hair brushes come in stiff and soft varieties that are made of nylon or polyester and can be used with acrylics or watercolour.
The eight common artist brushes are flat, bright, round, rigger, angle, filbert, fan, and mop. The following is the common usage:
Bright—good for impasto work
Flat—good for bold strokes and coverage
Mop—good for blending and glazing
Round—good for outlining and detail work
Angle—good for curved strokes and filling corners
Filbert—good for blending and detail work
Fan—good for blending, smoothing, and feathering
Rigger—good for fine lines