Here is a version of the car that demonstrates velocity rather than speed. You can see when you drive that there is an orange arrow on the car that grows when it speeds up. The arrow is a Vector to represents the velocity of the car. The vector points in the direction of motion and the length of the arrow is the speed.
Velocity can also be represented by velocity components - xVelocity and yVelocity. They are the amount of velocity in the x and y directions. To see what these look like, click on the "components" button.