From VEX Wiki
Spur gears are the simplest, and probably most common, type of
gear. They are used primarily to transfer speed and torque between parallel shafts. Their general form is a cylinder or disk. The teeth project radially, and with these "straight-cut gears," the leading edges of the teeth are aligned parallel to the axis of rotation. These gears can only mesh correctly if they are fitted to parallel axles.
See Also
