“LWIR” is an acronym for “Long Wave Infrared”, it’s on the invisible part of the electromagnetic, or more specifically, the infrared spectrum, and has a wavelength ranging from 8μm ~ 14μm. LWIR cameras and sensors, on a simple rundown, are designed to detect and capture infrared radiation, which is unseeable to the naked human eye, within that IR band.
Long-wave Infrared has considerably lower frequencies and carries less energy than visible light, and is not as harmful as ultraviolet or X rays:
LWIR cameras are mainly used in thermal imaging and security applications like leakage/gas detection, heating/cooling inspection, chemical/aerial/medical thermography, non-contact material testing, etc.