The American Marketing Association defines market research as “The systematic gathering, recording, and analyzing of data with respect to a particular market, where market refers to a specific customer group in a specific geographic area.”
The AMA's dictionary of marketing terms is posted on their Marketing Power webpage
This guide provides an overview of the secondary marketing literature. It provides tips and techniques for finding this literature from a variety of sources including trade organizations, the business press, journal articles, government and private data resources.
Secondary Data is often defined as "statistics not gathered for the immediate study at hand but for some other purpose”. When using secondary data, it's important to evaalutate the data in terms of your particular research need. Other things to consider are suggested by this list from FactCheck.org.
Guide to Testing Evidence
Is the source highly regarded and widely accepted?
Is the source an advocate?
What is the source’s track record?
What method is used?
Does the source “show its work”?
Is the sample random?
Is there a control group?
Does the source have the requisite skill?
Have the results been replicated, or contradicted?
Source: FactCheck.org
These are intended as representative examples of reports and studies that have content useful for marketing research. These reports are typically sponsored by organizations and marketing firms. They are often referred to in articles in the business press but also can be found using tools such as Google Advanced.