Dumb question on Extents

[Cameron Shorter]

Hi,

I'm having problems getting my first map to come up.  So far all I'm
getting is a blank page, which raises the following questions.  (Please
excuse me, but I have no GIS training).

* What are the units of Map Extents, and what are they relative to?

* Given a shapefile, how do I determine the Extent of the data represented
in it?  I've tried working this out with ArcExplorer, but I'm stumbling
over units.  Hence the previous question.

* It would be good if there was an explanation of what the fields in the
logs mean (although I think I've guessed most of the fields).

* Are there any other debugging tools around that I should know about?

Cameron Shorter
61.2.9901-1596 work.