Solar radiation is a general term for the electromagnetic radiation that is emitted by the sun. While the sun emits energy at a wide range of frequencies, peak radiance is within the visible range of the spectrum.
Solar radiation has a spectral, or wavelength, distribution that corresponds, roughly, to a black body curve of the sun's surface temperature. A black body curve graphically represents radiation coming from a "perfect" emitter across a range of wavelengths, based on temperature. Short wavelength radiation has a higher energy than long-wavelength radiation.