Microsoft Access creates the data source containing the field names and all the data from your table.
Note In a Word mail merge data source, the first record in the file contains the field names and is called the header row. All succeeding records are the data rows. The field names in the header record must match the field names in the main document. If they don't match, edit the field names either in the data source (you can open the data source in Microsoft Word) or in the main document so they do match.