Both Google and Yahoo! let you write a “map” of your website and submit it to them, so their spiders will know in advance exactly what to go index and how often. This has nothing to do with your website’s “Sitemap” page, those are for a human being’s eyes, although technically those make it a little easier on the spiders as well.
Google’s spider map is commonly a file named “sitemap.xml” that must be placed on the main web directory of your server host. Google demands that it be written in the XML language, which looks a lot like HTML except for a few other commands. Don’t worry, you won’t have to write a single line of code for this. There’s an excellent free tool coming up in a minute to write these for you.