The term "hood" and "shade" are often used interchangeably. The basic purpose is to block unwanted light from entering the lens which can cause lens flare and other anomalies. It is important to use a hood or shade designed for the widest focal length of the lens. A deep hood or one without sufficient diameter may cause vignetting.
A lens "hood" is usually round or rectangular and protrudes from the lens. You'll need to determine if your lens can accept a standard lens hood; not all lenses have threads for mounting accessories to the front of the lens. Some may require a special mounting and are generally available only form the lens or camera manufacturer.
A "shade" can be anything that shades or "flags" light from entering the lens. Shades can be found on matte boxes or fitted from improvised materials such as construction paper or aluminum foil or you can use your hand.
Most lens hoods are relatively inexpensive; matte boxes are often very expensive in comparison. You can usually find the universal type of lens hood at most pro camera shops. But if your lens requires one of the fitted types, you may need to order it through a dealer that carries that brand of camera/lens.
-DH
