Radiation is the form of heat transfer in which the heat flows from a hotter body to a colder body, without heating the medium. The heat that is transmitted in this fashion is known as radiant heat.
We receive sunlight in the form of radiant heat. When the radiant heat falls on a body, part of it is absorbed and the rest of it is reflected back. The absorption of radiant heat by a body depends on its absorptive, reflective and transitive properties. These properties are a function of the nature and color of the body. For example, a black body (or a body painted black) will be able to absorb more heat as compared to a shiny silver surface. Similarly, white colored surfaces absorb less heat and that's why white or light colored clothes are preferable in summers.