Both Velocity and Acceleration define of an object's rate of motion.
Velocity defines how fast something is moving and, is measured in ft/sec, mi per hr, etc.
Acceleration defines how fast the rate of speed (Velocity) is changing. When you push in the accelerator on a car, you make it go faster.
Acceleration is measured in ft/sec/sec. OR how many ft/sec faster is it moving for every second that the acceleration is applied.
EXAMPLE: The Acceleration due to Gravity is 32 ft/sec/sec.
When you drop something, first released it starts to fall with 0 velocity; after one sec, is it falling at 32 ft/sec; after two seconds is it falling at 64 ft/sec., etc, etc, etc.
Accel means even better.
The fastest production scooter in the world is the Vespa 946 Emporio Armani, with a top speed of about 57 mph (92 km/h). Racing scooters may achieve higher speeds, but they are not typically available for purchase by the general public.