Welcome Marlene!

I am somewhat confused, sorry. What made you decide to visit the Loire Valley, when you don't know anything about it? Are you booked on a tour?
As suggested before, get a travel book about the area, do some search in the net.
You can always come back for specific questions, but so far, you are just too vague.

Here's some reading about the famous Loire Castles:
http://perso.wanadoo.fr/chateauxdelaloire/indexanglais.htm