Hi.
In the core of the Sun energy is produced by what is called nuclear fusion - the extreme pressures at the sun's core are enough to push atoms together until they produce heavier atoms and energy. This is very important because it is what makes the Sun shine and makes it possible for there to be light and life here on Earth.

That energy makes its way outwards in the sun until in the outer third or so there are huge masses of hot material that rise up to the sun's surface, cool, and sink back down. There are other flows in this part of the sun as well that ultimately lead to the solar cycle - the change in solar activity that occurs about every 11 years.

Some places where you can find out more:
https://www.thesuntoday.o...sun/solar-structure/
https://www.windows2unive...ar_interior_new.html

Terry