A frame is a region in a browser window that can display an HTML document independent of what’s being displayed in the rest of the browser window. Frames provide a way to divide a browser window into multiple regions, each of which can display a different HTML document. In the most common use of frames, one frame displays a document containing navigation controls, while another frame displays a document with content
A frameset is an HTML file that defines the layout and properties of a set of frames, including the number of frames, the size and placement of the frames, and the URL of the page that initially appears in each frame. The frameset file itself doesn’t contain HTML content that displays in a browser, except in the noframes section; the frameset file simply provides information to the browser about how a set of frames should look and what documents should appear in them.
To view a set of frames in a browser, enter the URL of the frameset file; the browser then opens the relevant documents to display in the frames. The frameset file for a site is often named index.html, so that it displays by default if a visitor doesn’t specify a filename.
The following example shows a frame layout consisting of three frames: one narrow frame on the side that contains a navigation bar, one frame that runs along the top, containing the logo and title of the website, and one large frame that takes up the rest of the page and contains the main content. Each of these frames displays a separate HTML document.