This enables you to present information in a more flexible and useful way. It can resize dynamically if the user changes the window's size. Frames enable you to do things that you couldn't do before. As the user navigates the site, the information in the other frames changes while that in the static frame does not.
Table of contents are more functional.
One frame can contain TOC links that, when clicked, display results in an adjoining frame. Some links from a frame can be loaded in a different frame, while others load in the whole window or in a different window. It's recommended to always give an alternative way of browsing a framed site. The simplest is to write an alternative non-frames entry page and link to it from the main, framed entry page. It's more complicated to write a framed site.