Can anyone explain what magnetic sheilding is? What is the actual physical difference between a shielded speaker and a non-shielded speaker? (I know that a shielded speaker will not interfere with a CRT TV but I want to know the physical difference -- i.e. if I took apart a shielded speaker and a non-shielded one what differences would I see)

A shielded speaker will have a special cover that covers the magnet assembly. It's just a metal sleeve that fits over the magnet.
Non-shielded speakers will show the exposed magnet.