Sun spots are areas on the surface of the sun of extreme magnetic activity. Very large ones have been known to cause significant solar storms and this one is quite large. You can see the “swirling” effect in the photo caused by the strong magnetic field lines much like those that you can observe when you use a magnet to align particles of graphite.
Here’s an interesting fact: The “black” spot on the sun is about as bright as a full moon. It’s only dark because the photos are taken with settings to make them stand out against the extremely bright background.
The black and white photo gives you a great sense of depth. These sun spots are 120,000 miles in width. Yeah, about halfway to the moon. No big deal.
A quick measurement shows both are about 200,000 kilometers (120,000 miles) across – fifteen times the width of the Earth! If one end were placed on Earth, it would stretch halfway to the Moon.