Great question!  Response lists are made up of responders to direct mail solicitations where a very specific act was done to be included on that list.  This may include a subscriber to a specific magazine such as Martha Stewart Living, a donor to an organization such as March of Dimes, a buyer from a catalog or website such as Sur La Table or a member of an organization such as The Nature Conservancy.  A compiled file includes names that were collected from a variety of sources which include public record data, newspaper clippings, online surveys, warranty cards, b2b directories, etc.  Compiled records generally include an unbelievable ability to segment and target to get to the right audience.  A consumer compiled database may include demographic info such as age, income, gender, homeownership, home value, presence of children, interest level data (pets, wine, sports, etc) and hundreds upon hundreds of other criteria.  A business compiled database includes an array of firmographic data that may include employee size, industry type (SIC Codes or NAIC Codes), sales volume, location type, number of years in business, franchise indicator, ICC filing data and other selections including the ability target specific titles at a business.