UVB is a band of ultraviolet radiation with wavelengths from 280-320 nanometers produced by the Sun.
UVB is a kind of ultraviolet light from the sun (and sun lamps) that has several harmful effects. It is particularly effective at damaging DNA. It is a cause of melanoma and other types of skin cancer.
The ozone layer protects the Earth against most UVB coming from the sun. It may also be helpful minimize one's exposure to UVB by wearing hats, sunglasses, and sunscreen.