Each can scroll independently and change independently. Furthermore, each mini-window can be programmed to interact with one other. This means that clicking a link in one frame can cause something to happen in another. Frames pages have their own special type of HTML document called a frameset. The frameset contains formatting code which tells the browser how to display the divided window.
Frames can greatly reduce download times, especially when it comes to re-used elements.
As long as an individual frame's contents remain on the screen, unchanged, nothing more needs to be downloaded from the server or retrieved from cache. When a link clicked in Frame A changes the contents of frame B, only the contents of frame b needs to be called from the server or cache. And the fewer requests that need to be made, the quicker the download. However, as you've probably already learned, nothing is that simple and straightforward when it comes to the web. Furthermore, each browser will display frames documents a little differently.