Before you start the mail merge process, you need to understand the two documents that make up a mail merge:
Main document ” This is the actual document that you are producing. It can be a form letter or label. The main document contains the text and formatting that stays the same for each copy of the letter, as well as merge fields , which "hold places" that tell Word where to insert individual pieces of information from the data source .
Data source ” This is the file that contains the data you will merge into the main document. It is organized into records , one for each recipient. Each record is composed of individual fields for specific pieces of information, such as first name, last name , address, and so on.