The Major Problem

 The big conflict in dance photography is that people are moving fast in a dark room.  Let's see why this is a problem:

1. The dancers are moving. Moving dancers means that, unless you can stop the motion with a fast shutter speed, your pictures will show blurred motion.  While this is sometimes artistic, it is often distracting.  In general, you need to use a 1/60 or faster shutter speed to freeze the motion of the dancers.

 2. The auditorium is dark.  This means that the camera will want to use a wide aperture and keep the shutter open for as long as possible to get enough light to make a good photo.

 So you can see that the main conflict is light-gathering effectiveness vs. shutter speed.  If you let an automatic camera decide, it will often gather enough light to make a good exposure, but will use a slow shutter speed which blurs the motion.