The document discusses Microsoft Word 2010's mail merge feature. Mail merge allows a user to combine a main document with a data source to automatically generate multiple personalized documents. The main document contains merge fields where variable information from the data source will be inserted. The data source contains the variable records and fields. Users can create and edit data sources, insert merge fields into the main document, and use the mail merge wizard to step through the merge process from selecting a data source to previewing and printing/emailing the merged documents.