The Layers of the Sun
The first three inner layers of the Sun all make up it's interior. None of which you can see by traditional means. Scientists have to use the new field of helioseismology (the study of the propagation of wave oscillations in the Sun) in order to observe these layers. The Sun's exterior is made up of its final two layers and can be observed through an assortment of telescopes.
The core of the sun is it's source of energy and where it is all formed. Because of all of the gas particle movement going on, it is also the hottest layer. It comes in at a whopping 27 million degrees Fahrenheit. It is also incredibly dense, because of how tightly packed the particles are, thus giving us the perfect environment for nuclear reactions. This happens because the intense heat destroys the internal structures of all the atoms and breaks it down to it's basic parts, protons, electrons and neutrons.
The neutrons leave the core quickly because of their lack of electrical charge, which leaves behind the positively charged protons and negatively charged electrons. The resulting neutral gas the electrons and protons produce is the plasma. Because the heat is so high, those left behind, have a high amount of thermal energy and that makes them bounce around all over the place, quite quickly. This in conjunction with the high density plasma created, cause them to slam into each other and make the nuclear reactions. These reactions or fusions are what provide the Sun with all of it's energy.
The Radiation Zone
Once all of this energy is produced, it needs a way to travel from the solar center to the outer regions. This brings in the radiation zone. The radiation zone is the region...