Phototherapy is a form of treatment that involves exposing the skin to ultraviolet light in order to improve various skin conditions. This treatment is commonly used for conditions such as psoriasis, eczema, vitiligo, and jaundice in newborn babies. Phototherapy works by slowing down the rapid growth of skin cells, reducing inflammation, and promoting the production of vitamin D in the skin. It is typically performed in a medical setting under the supervision of a healthcare professional to ensure safety and effectiveness.