there are many types of animations that can be done however in PD Pro, from drawing frame by frame traditional animations (aka old-school anims) to using filters across the movies and animated brushes to compose more video over video, as well as post work over animations.

www.thebest3d.com/dogwaffle/art/animations

shows just a few examples

some start from next to nothing, e.g. apply a transformation to a still image to turn it into a movie clip, then add rain or lightning effects for more drama. Others started from Carrara renders or Bryce and more, and again did some magig with filters across the timeline.  Then there's also those who know how to draw and create an animated cartoon.

It's a bit different at that than, say, using a 2D animation system which is object oriented with bones and keyframes of the object's transforms and stuff, like Moho or FLash, it's a bit more like Flipbook I guess. But it does go further in the sense that while everything is based on rasters and sprites, you can load a sprite and even an animated sprite or avi or image sequence into the brush and then keyframe the path of the brush across the frames of your animation-to-be.