Infrared radiation is a natural form of radiation which accounts for nearly 50 % of the total radiation spectrum of the sun. When infrared radiation comes into contact with our skin it triggers a pleasant warming sensation. This is why it is also affectionately known as "heat radiation". Without the daily dose of infrared radiation from the sun there would be no life on Earth.
Thanks to its wavelength short-wave infrared radiation penetrates the atmosphere particularly well, regardless of the air temperature. This explains why we feel a pleasant warmth in the sunshine during winter, despite a relatively low external temperature.