Remember photons and how they can transport energy and also transfer energy to atoms. Atom absorbs photon, but only photons of certain energies can be absorbed for each type of atom. Atom absorbs photon, re-emits it in a random direction. After the collision, photon will have new direction. The random walk area is called the radiation zone .
Energy is transported by photons.
When the temperature of the gas has dropped to about 2 million K, photons can start being absorbed by ions rather than bounced by electrons heat is built up by photon absorption. Very efficient method of energy transport. The Sun's surface Hard to define since the Sun is a gas. Photosphere is where photons can escape more easily without further interaction. Peak energy comes out about 510 nanometers, green light.