The shortest wavelenghts of infrared radiation are also the nearest to the visible light. That is why it is called as Near InfraRed radiation (NIR). Near infrared radiation is a part of electromagnetic radiation as well as visible light or thermal radiation, but it can not be seen or other wise senced by humans. Because of this, near infrared imaging may see targets and phenomena that cameras working with visible light wavelengths can not see or things that people can not sence.
NIR imaging is used among others in pharmaceutical and food industry for example defining water content and moisture. Respectively, moisture content is a significant indicator of process control and quality for example in agriculture, textile industry and forest industry.
There are also materials that look very different with near infrared imaging than with visible wavelenghts. This feature can be used for example in imaging through materials that are non-transparent in visible light imaging.