Sketchcast lets you draw a simple drawing on a page which is animated upon playback. You may add voiceover which would help a great deal in truly trying to explain a concept.
Drawings are more effective than words since the stylus does not make for tidy printing or writing.
You could use this as you would a single slide, or for advertisement of an event, or for a cartoon which would draw itself before your eyes.
Here is my second effort (I deleted the first which was all scrawling text.)
Cut into pieces
Plant eyes up
In a trench