A cache (pronounced “cash”) is a storage area for computer files. Google maintains an enormous cache of Web pages. Actually, for practical purposes, it doesn’t matter whether you confuse them or not, but they are different.

The index is a database of Web page content, stripped of its formatting. The cache contains the pages themselves. By and large, clicking the Cached link provides a quicker display of the target page because you’re getting it from Google’s computer instead of from the Internet at large.

So why would you ever not use the Cached link instead of the main page title link? Mainly because the cached page is not necessarily up-to-the-minute, especially with pages that change frequently (such as Weblogs and news sites). If you view the cached version of a page that you know changes frequently and is dated, such as the front page of a newspaper site, you can see that Google’s cache is a day or more behind. For users without high-speed Internet access, it’s more convenient to pull from the cache when looking for a big page (about 50K or so) that doesn’t change much. You might also use the Cached link if the page title link refuses to display the page for some reason.

One disadvantage to pulling up a cached search result is the Google notice that appears atop all cached pages. That is one bulky notice, taking up about two vertical inches of screen space on a screen resolution of 800 x 600. Besides being an eyesore, the notice sometimes makes additional scrolling necessary if you want to see the entire page. If you get tired of the notice, click its link to the uncached page.

The cache link comes in handy when you want to take a brief trip back in time, to view a Web page that you know has changed or has been taken away. Once, David Letterman, on his late-night show, complained that the CBS site displayed a picture of Letterman’s rival, Jay Leno. Letterman’s show is taped in the afternoon, and by the time the show aired CBS had removed the offending image. Many people, including myself, wanted to preserve the amusing gaffe, and we did so by calling up the old page in Google’s cache.