Frames are a powerful feature in webdesign when used correctly. Visually they are barriers and act , or can act much like table borders. Usually they seperate rather than integrate. Frames are not HTML and therefore spare a thought and make provision for the person unable to view frames. You can do this with an alternative HTML environment.

Basically they allow you to subdivide the browser window into areas which can be used for the following three major purposes:

The use of indexes (like in this setup)

The ability to create a hierarchy in the site design

To lift out a seperate window to read and then click away (see example)