Mail merge is for simplifying repetitive documents and tasks. Mail merge can be used for creating many documents at once that contain identical formatting, layout, text, graphics, etc., and where only certain portions of each document varies. Mail merge is also used for generating mailing labels, envelopes, address lists, personalised training handouts, etc. As well as hard copy mailshots, it can be used to generate multiple emails and electronic faxes. And it can even be used to create a 'friendly' front-end to spreadsheet or database information.
Melton, Beth and Dave Rado. Word MVP Site, The (2005). Articles>Word Processing>Databases>Microsoft Word