Bevel gears are of help when the direction of a shaft’s rotation needs to be changed. They are often installed on shafts that are 90 degrees apart, but can be designed to just work at other angles as well.
The teeth on bevel gears could be straight, spiral or hypoid. Right bevel gear teeth actually have the same issue as straight spur gear tooth — as each tooth engages, it impacts the corresponding tooth all at one time.
Exactly like with spur gears, the solution to the problem is to curve the gear teeth. These spiral tooth engage just like helical teeth: the contact starts at one end of the gear and progressively spreads over the whole tooth.
On straight and spiral bevel gears, the shafts must be perpendicular to each other, but they must also maintain the same plane. If you were to lengthen the two shafts past the gears, they might intersect. The hypoid gear, on the other hand, can build relationships the axes in different planes.
Hypoid bevel gears in a car differential
This feature can be 
used in lots of car differentials. The band gear of the differential and the insight pinion equipment are both hypoid. This allows the input pinion to be installed less than the axis of the ring gear. Figure 7 displays the insight pinion engaging the band gear of the differential. Because the Liquid-ring Vacuum Pump driveshaft of the car is connected to the input pinion, this also lowers the driveshaft. This implies that the driveshaft doesn’t intrude into the passenger compartment of the car as much, making even more room for people and cargo.