This chapter moves from observation of the sun into the inner workings and how it all is thought to work, and what we can deduce. Things like models of the interior and how well they compare with measurements. Radiative and convection zones, stellar "earthquakes" and so on all feature.
Also covered are some of the reasons for the more visible things such as prominences and mass coronal ejections - which includes some tricky magnetic field stuff.
Finally the sunspot cycle and the 22 year general cycle.