Similar to infrared light, UV energy is related to visible light. IR is next to the red end of the light spectrum and represents a lower energy level than visible light.
UV light is more energetic than visible light and is above blue and violet in the light spectrum. UV energy is not all the same. UV light can be partitioned into categories of how it affects animals and plants.
UV-A light is slightly more energetic than visible blue light in the spectrum. UV-A is commonly known as “black light.” Many plants use this energy for healthy growth. UV-A, in modest amounts, is responsible for skin tanning. This is the light that is recommended for UV cure paints.
UV-B is at higher energy levels then UV-A. UV-B energy is high enough to cause sunburn (erythema). Natural sunlight at ground level contains both UV-A, and some UV-B light waves.
The highest energy UV light is labeled as UV-C light. Light energy of this level can be used to sterilize things. Obviously no person should be exposed to UV-C energy. Although the sun gives off UV-C energy, the upper atmosphere filters this out, so we are not exposed to UV-C from sunlight on earth.