There are three main parts to the Sun's interior: the core, the radiative zone, and the convective zone. The core is at the center. It is the hottest region, where the nuclear fusion reactions that power the Sun occur. Moving outward next comes the radiative (or radiation) zone. Its name is derived from the way energy is carried outward through this layer, carried by photons as thermal radiation. The third and final region of the solar interior is named the convective (or convection) zone.

Source: University Corporation for Atmospheric Research