Hi Rick.
We think sunspots are made when bundles of magnetic field come up from inside the Sun and break through the Sun's surface. We can measure that the magnetic field in Sunspots is higher than other places on the Sun and we are starting to be able to observe what goes on beneath them too.
(See
http://sohowww.nascom.nas...hotshots/2001_11_06/
http://sohowww.nascom.nas...hotshots/2001_12_10/
for some pictures)

We think that sometimes these bundles are simple loops resulting in simple sunspots.
Sometimes they are complicated clusters of loops, though, resulting in complicated sunspot clusters. Why that should be we don't know and we'd like to find out. Complicated clusters of sunspots are much more likely to be associated with major solar activity like coronal mass ejections and large flares.

Terry