The image of the sun shown below illustrates 3 parts of the Sun's structure.

The core is the innermost 10% of the Sun's mass. It is where the energy from nuclear fusion is generated. Because of the enormous amount of gravity compression from all of the layers above it, the core is very hot and dense. Nuclear fusion requires extremely high temperatures and densities. The Sun's core is about 16 million degrees hot and has a density around 160 grams/centimeter3. This is over 20 times denser than the dense metal Iron which has a density of "only'' 7 grams/centimeter3. However, the Sun's interior is still gaseous all the way to the core because of the extreme temperatures. There is no molten rock like we find in the interior of the Earth.

The radiative zone is where the energy is transported from the superhot interior to the colder outer layers by photons. Technically, this also includes the core. The radiative zone includes the inner approximately 85% of the Sun's radius.

Energy in the outer 15% of the Sun's radius is transported by the bulk motions of gas in a process called convection. At cooler temperatures, more ions are able to block the outward flow of photon radiation more effectively, so nature kicks in convection to help the Sun transport its energy. This part of the Sun just below the surface is called the convection zone.