What is infrared thermography?
Infrared is an invisible portion of the light spectrum extending from 0.75 to 1000 microns. All objects warmer than absolute zero (0 Kelvin or -275.15°C) emit energy somewhere within that range. The warmer the object, the brighter we see it in our thermal camera. White is hotter, black is colder.

Links:
IRINFO.ORG
IPAC - NASA's multi-mission center of expertise for long-wavelength astrophysics
Temperature.com Inc.

What are some of the other applications of thermography?
Airborne applications
Brake and engine systems evaluation for perfomance and cooling efficiencies
Cold storage cooling losses.
Covert surveillance
Dentistry, tempromandibular jaw disfunction and more
Design proto typing evaluation
Diseases evaluation, breast cancer, arthritis and many more
Electrical motor inspections, mechanical bearing inspections
Environmental inspections, pollution dumping, thermal dumping of waste water
Fire mapping, hold over fires, fireline and mop-up inspections
Flame propogation explosion analysis.
Furnace internal flame evaluation and tube inspections
Furnace refractory (insulation) inspections
Heat exchanger quality and efficiency evaluation
High voltage aerial electrical inspections for transmission lines
Medical injury examinations for whiplash, back injuries, Carpal Tunnel
Motor racing suspension and tire contact diagnostics
Overhead urban and rural distribution electrical inspections
Pipeline inspection, leak detection, stress corrosion cracking areas
Power generation generator inspections.
Power plant boiler flue gas leak detection
Printed circuit board evaluation and trouble shooting.
Refinery process evaluation
Refinery process line insulation loss or leak detection
Research and development applications
Search and rescue
Sports injuries and evaluation, and therapy progress
Substation electrical inspections, tranformers and capacitor evaluation