A mail merge is a capability of database software, word processors, and some e-mail programs. Mail merge takes a standard form and formats it with unique fields such as e-mail address, name, address, phone number, and other information to make the message look unique for each person in a database, CSV, or another source of input.
Example of a mail merge
For example, a standard mail merge form may look like the example below. In this example, each of the bracketed words (e.g. [address]) are the fields merged during the mail merge.
We would like to thank you [username] for purchasing our product.
With a program capable of mail merge, the program would pull the personal information and place the appropriate information into the above fields. So, one of the final outputted or sent results may look like the example below.
1234 some street
City, State Zip
Dear Bob Smith,
We would like to thank you Bob Smith for purchasing our product.