Night vision is basically a technology which allows one to see in the dark.
Originally, it was developed for military use but now the most common applications include night driving or flying, night security and surveillance, wildlife observation, sleep lab monitoring and search and rescue.
Generally, there are 3 types of night vision technology-low light imaging, thermal imaging and near infrared illumination.
Low-light imaging is used to improve visibility in dimly lit environments. It uses a device called an image intensifier to amplify available light.
Thermal imaging is a method of improving the visibility of objects in a dark environment by detecting the objects' infrared radiation and creating an image based on that information. It is generally used for military purposes.
Near-infrared illumination is a method of night vision wherein a device that is sensitive to invisible near infrared radiation is used in conjunction with an infrared illuminator. It is used in perimeter protection and camcorders.