What exactly is infrared, or radiant heat? No need to worry - it has nothing to do with either ultraviolet radiation (which gives you a sunburn and damages your skin) or atomic radiation (the kind from a nuclear bomb).
Radiant heat is simply a form of energy that heats objects directly through a process called conversion, without having to heat the air in between. Radiant heat is also called infrared energy (IR). Our sun is the principal source of radiant energy that we enjoy daily (some more so than others).
Have you ever been outside on a partly cloudy spring day of about 50 degrees F. and felt quite comfortable until the sun was suddenly obscured by a cloud? Although the air temperature had not had time to drop, you felt chilled, as the cloud would not let the warming infrared rays through to reach you.