Gears certainly are a crucial component of many motors and devices. Gears assist in torque output by giving gear reduction plus they adjust the direction of rotation like the shaft to the trunk wheels of automotive automobiles. Here are some basic types of gears and how they will 
vary from each other.
Spur gears are mounted in series on parallel shafts to achieve large gear reductions.
The most typical gears are spur gears and are used in series for large gear reductions. One’s teeth on spur gears are straight and are mounted in parallel on different shafts. Spur gears are used in washing machines, screwdrivers, windup alarm clocks, and other devices. They are particularly loud, due to the equipment tooth engaging and colliding. Each impact makes loud noises and causes vibration, which explains why spur gears aren’t used in machinery like cars. A normal equipment ratio range is 1:1 to 6:1.
Helical gears operate more smoothly and quietly compared to spur gears because of the way the teeth interact. One’s teeth on a helical gear cut at an angle to the facial skin of the apparatus. When two of one’s teeth start to engage, the contact is gradual–starting at one end of the tooth and maintaining contact as the gear rotates into complete 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 is the most commonly used gear in transmissions. They also generate large amounts of thrust and make use of bearings to help support the thrust load. Helical gears can be utilized to change the rotation angle by 90 deg. when mounted on spiral bevel helical gearbox perpendicular shafts. Its normal equipment ratio range is 3:2 to 10:1.
Bevel gears are used to change the direction of a shaft’s rotation. Bevel gears have tooth that are offered in straight, spiral, or hypoid shape. Straight teeth have similar features to spur gears and also have a large influence when involved. Like spur gears, the normal equipment ratio range for straight bevel gears is 3:2 to 5:1.
Spiral teeth operate exactly like helical gears. They produce less vibration and sound when compared to straight teeth. The right hand of the spiral bevel is the outer half of the tooth, inclined to visit in the clockwise direction from the axial plane. The left hands of the spiral bevel travels in the counterclockwise path. The normal equipment ratio range is 3:2 to 4:1.
In the hypoid gear above, the larger gear is called the crown while the small gear is named the pinion.
Hypoid gears are a type of spiral gear in which the shape is usually a revolved hyperboloid instead of conical shape. The hypoid gear areas the pinion off-axis to the band gear or crown wheel. This allows the pinion to end up being larger in diameter and provide more contact area.