G5.3 bulb base consist of 2 short pins 5.3mm apart from each other. It is the standard pin for a halogen bulb. There are other bulb base type standard, GU10 which is more secure and not easily detected like the G5.3 pins. MR16 specify the size of the bulb shape.
MR16 G5.3 bulb is quite popular and is commonly known as a spotlight. It is commonly implemented with a halogen bulb which can generate very very bright light. Halogen similar to the incandescence which generates light by heating up an element. This means it very very hot. Be careful when handling a halogen bulb. Allow a period of time for the bulb to be cool before any replacement. Never touch the halogen glass, as our hand can leave a trace of oil on the surface which can break the bulb with the heat. Wipe the bulb if the bulb is touched by your bare hand. The power consumption is very high from halogen. Changing a halogen or incandescence bulb to a LED version, you can easily get 10 times energy saving. 40-50W halogen to 4-10W LED.