Normalization is a method of break down complex table’s structure into simple table structure by using certain rules.
http://www.mindstick.com/Articles/88d5a271-b369-4c0a-ae80-01e66df98b6a/?What%20is%20Normalization

Denormalization is a technique to move from higher to lower normal forms of database modeling in order to speed up database access. Denormalization is usually done to decrease the time required to execute complex queries.
http://www.mindstick.com/Articles/2168d768-017c-41f4-a7a3-ac76faabb48d/?Denormalization%20in%20SQL%20Server