MVVM (stands for Model-View-ViewModel) is a well-known architectural pattern in the world of WPF. Most enterprise level WPF applications are MVVM-based. Learn deeply the concepts lying behind the MVVM pattern in order to understand what MVVM is in essence and how to pragmatically apply it to a WPF application. This is a great MVVM tutorial for beginners (beginners in MVVM, don't forget to look at prerequisites)!