This is nothing different from a document file, but you can work on it to publish on web directly as a web form template. This one is the latest feature of word. You have several integrated programs to improvise your templates in terms of visual appearance. You also have the option to work with the add_ons in MS word. If you work wisely, you can bring out a professional template all by yourself.
Templates have many faces and styles. Some are specific to an industry. Use these templates as guides in drafting your own letter.