Use templates to create documents for your site that have a common structure and appearance. Templates are useful if you want to make sure that all of the pages in a site share certain characteristics, regardless of whether you are creating a new site or updating an existing site. Rather than setting the correct properties for every new page, or making changes to every single page, use a template to make changes to several pages at once.
When you create a template, you can indicate which elements of a page should remain constant (noneditable) and which elements can be changed. For example, if you are publishing an online magazine, the masthead probably won't change, but the title and content of the feature story will change in every issue. To indicate the style and location of the feature story, you can use placeholder text and define it as an editable region. To add a new feature article, the writer just selects the placeholder text and types the article over it.
You can modify a template even after you have used it to create documents. When you update documents that use the template, the noneditable sections of those documents will be updated to match the changes to the template.
Click Show Me for an animated introduction to using templates in Dreamweaver.