A document that contains parameters, identified by some special syntax, that are replaced by actual arguments by the template processing system. For example:
Dear , would like to invite you
to a party at on at .
Where the words in angle brackets are the parameters to be replaced by the name of an actual guest, etc.
More sophisticated systems allow repetition, where a section is repeated in a single output document using a list of inputs; conditional sections or (nested) inclusion of other templates.
See also class template.