Silverlight uses timeline concept for animation (not frame based, used by Flash). There is a StoryBoard at the heart of every animation here. StoryBoard can contain one or more Key Frame elements.
There are 4 type of Key Frames here:
1. Linear : Moves from the starting state to the end state in a smooth, linear fashion.
2. Discrete : Jumps from starting state to end state instantaneously.
3. Spline : Moves from the starting state to the end state varying speed based on mathematically defined curve.
4. Easing : A more evolved version of Spline, moves from the starting state to the end state based on a easing funcation.
