Catalog mailing list

I am a relatively new user to Netsuite (2 months), so pardon me if this has been asked before, but I cannot find an answer.

We send out catalogs to all of our customers who have purchased from us in the  ast 24 months.  I need create a report that filters my customer list so I only see the customers that have placed and order in this time period so I can export the list and hand it over to the company that handles the mailing for us.

When I try a customer search, there are multiple date fields to to filter on, but none appear to give me the date of the most recent order.  That also brings up another question.  Where can I find a listing of what criteria these date fields represent?  For instance, if I do a customer search on transaction fields, one field I can filter on in "date".  My question is, date for what?  Is the the order date, the ship date, the customer creation date, or some other date.