In plain English, OLAP as it applies to MapPoint is geographic data mining, aggregating to different levels of detail.

As an example (what I think jetski is trying to do):
You want to see sales by state,
then zoom in to an under-performing state to see what counties did poorly,
then zoom in on a county to see how each zip code affected sales.

Several definitions are here: http://www.google.com/search?q=define%3Aolap