The layout of normal website pages is far better and easier done with tables. But there are situations where their use is acceptable or even unavoidable. Like for instance when you want to show a set of external links and the linked pages at the same time. Switching back and forth would be the only other option. Which may be quite cumbersome.
Frames are a construct to show several web pages in one browser window.
You create a page with sub windows, in which you show other pages. Those other pages may contain yet other framed pages. To understand frames, it is very important that you grasp this concept. A frameset page is different from a normal web page. It does not have a BODY, like a normal web page would.