Take a look at this very detailed article in which Anjaiah Keesari discusses the basic concepts of Animations in Silverlight applications.
In this chapter, you will be learning the basic fundamental concepts of Animations in Silverlight Application, which includes Animation Types, namespace details, classes, objects used, implementation of different types of animations with XAML and with C# code and some more interesting samples for each animation. You will see how to use important properties of Timeline class with examples, controlling animation with storyboard methods. We will also see Animation in XAML versus Animation in Code with an example.