A differential (In automotive applications, the differential housing is sometimes colloquially called a “pumpkin”) is a device or tools, generally not necessarily or needed employing gears, differential is capable of transmitting rotation and torque (Torque is supplied from the engine, via the transmission, to a drive shaft) through three shafts, many activity almost always used in one of two ways. It receives one input and provides two outputs. This method usually found in automobiles. Other ways, it combines two inputs to create an output that is the sum, difference, or average, of the inputs.
In automobiles or other wheeled vehicles, the differential allows each of the driving roadwheels to rotate at different speeds, while for most vehicles supplying equal torque to each of them.
From searching in internet
I found two types of Differential Gears
there are two design differences in the differential gears. There are spiral and hypoid gears. Spiral differential gear the pinion gears contacts the ring gears at its centerline. Different with hypoid gear. In the hypoid the pinion gear contacts the ring gear below the centerline
Source pictures and references : Wikipedia.org