How do I use Mail Merge in Microsoft Office Word?
Mail Merge Information
In Microsoft Office Word, you can create envelopes using the mail merge feature. A mail merge involves merging a main document with a data source. A main document contains text and other items that remain the same in each envelope. A data source contains the information that changes in each envelope , such as the name and address of each recipient.
Merge fields, which you insert into the main document, instruct Word where to print information from the data source. When you perform the mail merge, Word replaces merge fields in the document with information from the data source. Each row in the data source produces and individual envelope
Please visit these websites for more detail
For Windows Office 2007 or 2010: http://support.microsoft.com/kb/826838/
For Mac Office 2008: http://support.microsoft.com/kb/275013