[Ifeffit] Principle Component Analysis

Hi all, I am trying to understand the method of Principal Component Analysis. What is PCA, On what principle it works, How it can be applied to system and to what type of system it can be applied. I am trying to find the answers of these questions. If someone can please tell me where I can find the literature related to these questions, I will be very thankful. with thanks Abhijeet Gaur