Frames allow you to divide the browser window into several independent, scrollable areas, each of which displays a different, unique HTML document. So you’re actually displaying several different web pages within one interface.
Frames allow more complex interactions to take place within the window of the browser, without completely reloading the page. One area of the page can remain static while another reloads, creating a more consistent visual environment. This same-page environment makes more complex interactions possible and helps prevent the disorientation so common on the web.