PE Router is a abbreviation for Provider Edge Router, that probably explains why it is used in a ATM circuit ;) There is a lot of information about this, and more subjects, on www.cisco.com. You can almost always find it with the search.
Information about ATM can be found here:
http://www.cisco.com/warp/public/614/12.html
and here:
http://www.cisco.com/en/US/tech/tk39/tsd_technology_support_category_home.html
I hope this answers youre question, if not, you can always post it on NetPro!
Regards,
Michaël