Heat radiation (infrared) and visible light are essentially the same, just different wavelengths. The respective photons come into being as elementary particles (electrons) drop to lower energetic levels after having been raised to higher ones previously by way of some excitement (for example thermal motion, being hit by other photons, etc). The photons pick up the difference in energy, the higher the energy conferred onto them the shorter their wavelength. Photons aren't propelled, they come into being at the speed of light.
That's what I remember from my school physics anyway
