What is a sun spot? What’s going on? What are the elongated things at its edge? What’s in its dark centre?
The dark area of the spot is significantly “cooler” than the surrounding bright surface area.
Very powerful magnetic forces in the dark area temporarily block the natural flow of interior heat to that part of the sun’s surface.
A sun spot is like a hole in the upper layers of the sun’s heliophere (like an atmosphere but composed mostly of hot plasmas instead of gas). It allows us to see beyond this outer layer and peer a little deeper into the heliosphere. So the dark spot is a deeper layer that we can’t normally see.
The “elongated things” are probably plasma filaments (think of the moving lines that radiate from a Van De Graaf generator, except multiplied by about a million times in number and intensity).
Another way to think of this is like a storm in the heliosphere, kind of like looking down into the eye of a tornado from above (or looking through Jupiter’s great red spot into a lower level of the atmosphere there). But that similarity is just superficial; sun spots are not caused by normal weather phenomenon, but by electromagnetic phenomenon.