1. Merge Field: A merge field is where you want to insert the information from a data source into a main document. Merge fields appear with chevrons (« »).
2. Data Source: Data source is a file that contains the names and addresses or any other information that vary with each version of a mail-merge document.
3. Main Document: Main document is the document which contains text and graphics. It may be a formal or an official letter.
4. Two types of data on which mail merge can be applied are Labels and Letters.