Many of the clients I talk with have an understanding that a Google sitemap is a way to positively impact your natural rankings. This of course is not true, the Google sitemap merely allows you to tell Google that you have the following web pages within your domain and that you would like them to be crawled. You have the ability to set how frequently the page is updated: Daily, weekly, or monthly. The last option you have within the Google sitemap is the option to set the priority of the page.
This is the webmasters way of telling Google which pages are more important than others. For example the home page would be more important than page to showcase links so it would receive a higher priority. Google will then access the Google sitemap you have uploaded and see the listings of pages and information you have provided. This will result in Google being able to find and index those pages faster and get a basic understanding of the structure of the website. This is not to say that Google wouldn’t find the pages of the website on there own, but it facilitates Google finding them faster.
Another misconception is between the Google sitemap and the Normal sitemap. The normal sitemap should be its own page and be linked from every page of the website. This page should include category and product levels of your website. By creating a sitemap you will be aiding in a couple of areas. The first thing you will be helping is the internal linking structure of the website. This will help the search engines see all the pages of the website. Another way you will be aiding is in the user experience of the website. A sitemap gives the user another method of browsing your website. The Google sitemap is an XML file which gets uploaded to the root directory. The Google sitemap will never been seen by the users, only by Google.
To recap, the Google sitemap is used for the sole purpose of telling Google what pages you have on your website, how frequently those pages are updated, and the priority of the page. This allows Google to find and index those pages more quickly than if the pages had to be found on their own. This is also true for the Yahoo sitemap, which follows the same standards as the Google sitemap. Both tell the search engine which pages are on the domain so it may be indexed quicker.