How fast is my CD-ROM Drive?
CAV is Constant Angular Velocity, which means the CD spins at the same speed (RPM) whether reading from the inside or the outside tracks. This means that the data at the outer edge of the disk will be read faster, because of the larger radius. Manufacturers are releasing some drives that are CAV or CAB/CLV combined, perhaps because it is cheaper to do. (These type do 8X on the inside and 12X on the outside.)
CLV is Constant Linear Velocity, meaning the spiral track is read at the same speed over the whole disk, which involves reducing the angular velocity of the disk as the head moves to the outer rim. This is the usual method of control, primarily a hang-up from the origins of CD. (You don't really want your music to speed up as you get to the end of the disk do you?)