Gears certainly are a crucial part of several motors and machines. Gears assist in torque output by giving gear reduction and they adjust the path of rotation just like the shaft to the rear wheels of automotive automobiles. Here are some simple types of gears and how they are different from each other.
Spur gears are mounted in series on parallel shafts to accomplish large gear reductions.

The most common gears are spur gears and are found in series for huge gear reductions. The teeth on spur gears are straight and are installed in parallel on different shafts. Spur gears are used in washers, screwdrivers, windup alarm clocks, and other devices. These are particularly loud, because of the equipment tooth engaging and colliding. Each impact makes loud noises and causes vibration, which is why spur gears aren’t found in machinery like cars. A normal equipment ratio range is 1:1 to 6:1.

Helical gears operate more smoothly and quietly in comparison to spur gears because of the way one’s teeth interact. The teeth on a helical gear cut at an angle to the facial skin of the apparatus. When two of the teeth start to engage, the contact is gradual–beginning at one end of the tooth and maintaining contact as the apparatus rotates into full engagement. The typical range of the helix angle is approximately 15 to 30 deg. The thrust load varies straight with the magnitude of tangent of helix angle. Helical may be the most commonly used equipment in transmissions. In addition they generate large amounts of thrust and use bearings to help spiral bevel helical gearbox support the thrust load. Helical gears can be utilized to adjust the rotation angle by 90 deg. when installed on perpendicular shafts. Its normal equipment ratio range is 3:2 to 10:1.
Bevel gears are accustomed to change the path of a shaft’s rotation. Bevel gears have the teeth that are available in straight, spiral, or hypoid form. Straight teeth have similar features to spur gears and possess a large effect when involved. Like spur gears, the standard gear ratio range for straight bevel gears is 3:2 to 5:1.
Spiral teeth operate exactly like helical gears. They create less vibration and noise in comparison with straight teeth. The right hand of the spiral bevel may be the outer half of the tooth, inclined to visit in the clockwise direction from the axial plane. The left hand of the spiral bevel travels in the counterclockwise path. The normal gear ratio range is 3:2 to 4:1.
In the hypoid gear above, the bigger gear is named the crown as the small gear is named the pinion.

Hypoid gears are a kind of spiral gear in which the shape is a revolved hyperboloid rather than conical shape. The hypoid equipment places the pinion off-axis to the ring gear or crown wheel. This allows the pinion to be larger in diameter and provide more contact area.