As the Sun collapses, the Helium will start to burn at the core and Hydrogen will burn in shells around the core, and the Sun will puff up into a Red Giant, so large that the Earth will be engulfed. When all the fuel is exhausted, the Sun will shrink down to a White Dwarf and slowly fade away. Meanwhile, cooler bubbles will sink. The process is very much like watching a boiling pot of water, but on a MUCH larger scale. The photosphere is the part of the Sun that we see.
Sunspots are probably the most remarkable feature associated with the photosphere.
Once astronomers had access to telescopes, they noticed that these spots moved slowly across the Sun, and so they could determine the rotation period of the Sun. Another discovery about sunspots is that they occur in cycles. The Sun's activity cycle is 11 years long. At the minimum of the cycle, there might be no sunspots at all. Sunspots are associated with high magnetic fields that somehow keep the heat away.