Mail merge lets you create a batch of documents that are personalized for each recipient. For example, a form letter might be personalized to address each recipient by name. A data source, like a list, spreadsheet, or database, is associated with the document. Placeholders--called merge fields--tell Word where in the document to include information from the data source.

You work on the main document in Word, inserting merge fields for the personalized content you want to include. When the mail merge is complete, the merge document will generate a personalized version of itself for each name in the data source.