what is a ground loop?

JeffreyBeyr-
This is one of the reasons it is most preferable to have dedicated lines for a listening room? So you can deal with the problem at its source? This makes more sense to me. Thank you!
Loonytunz- my cats totally approve of your analogy!

Eldartford,
Thank you. I actually did search the archives, but the language used is sometimes difficult to sort through. Language that leads to other language- an abundance of all that, but still meaning is more difficult to come by. I appreciate your time.