You can write macros that do most things you could do manually and a
few things that you can't do manually.
Understand that your question is very general, a lot like asking "What
kind of things can you say in English?"
If you need a more specific answer, try a more specific question.
We'll be happy to help if we can.
==============================
PPT Frequently Asked Questions
http://www.pptfaq.com/
PPTools add-ins for PowerPoint
http://www.pptools.com/