powerpoint is a presentation program,the sort of thing you have when you
speak to a group of people and have data or pictures to support you.With a
data projector you can have very nice "pictures" shown on a screen to
illustrate what you are talking about.
Excel is a spreadsheeting program with built in functions and programming
abilities .Most people think of excel as a accounting type tool.You can use
it as a simple phone number book with names and number typed in the
preformatted colums and rows...and from there the sky is (almost)the
limit......