VARIATIONS
An accessory drive belt is generally either a V-belt or serpentine
belt. An engine will have one type or the other, but not both. A drive belt
can also be cogged.
V-belt has a "v" shape when viewed from side. These belts are usually used in sets of 2 or 3 to drive all engine component accessories. The V-shaped belt and pulley contact area provide friction necessary to drive the accessory. The V-belt can only drive pulleys from its side surfaces.
V-BELT
Serpentine (Ribbed) belt is a long belt with multiple ribs on the inner surface. These multiple ribs provide additional frictional contact area to drive the accessory. The belt is relative thin but extremely flexible like a snake (or serpent). The pulleys that are driven by a serpentine belt must all be in the same plane. The belt can drive pulleys from both its top and bottom surfaces.
SERPENTINE (RIBBED) BELT
Cogged belt has built-in notches, or teeth, on the bottom surface to prevent the belt from slipping. Timing belts are typically cogged.
COGGED BELT
