About half of the suns radiation lies in the visible spectrum...
The other half mostly in the near infrared part.
Digital camera sensors are able to capture some of that light.
Replacing the infrared blocking hotmirror filter with an infrared filter allows digital cameras to capture images in the near infrared spectrum. Depending on the specific filter, sensor and white balance setting the resulting images show "false" colors that can be further adjusted in an image editor.
