Frames commonly define a navigation area and a content area for a page.
When you split a document into frames, Dreamweaver creates an untitled frameset file and untitled documents in each of the new frames. A frameset is a file that defines a web page with frames. A frameset stores information about the size and location of the page's frames along with the names of the files that should be loaded as the content for each of the frames. When frame borders are displayed, Dreamweaver adds space around the document for the border and widens small borders for easier dragging and selecting.