Using the concept of templating in the browser is becoming more and more wide-spread. Probably the main reason to this is the move of application logic from the server to the client, in tandem with the increasing usage of the MVC pattern. Templates can be extremely useful in client-side development, especially to separate markup and logic in views.
There are plenty of definitions of the term "template", here is a good one from foldoc (http://foldoc.org/template):
A document that contains parameters, identified by some special syntax, that are replaced by actual arguments by the template processing system.