Seriously, just do a Google search. Top results for "periodization":
http://www.unm.edu/~lkravitz/Article...odization.html
http://en.wikipedia.org/wiki/Periodization
http://www.trifuel.com/training/tria...w-does-it-work
There isn't one definition or method of periodization. It depends on the sport. Oh, but you know better.
As it pertains to weight/strength training I suggest you read this book:
http://www.amazon.com/You-Are-Your-O.../dp/0971407614