A sitemap is how you tell search engines what pages are available for crawling on your website. A sitemap is an XML file that lists all the urls for your website.
Sitemaps should also by dynamic (changed daily!), and not a static file created once in a while by your website or SEO provider. Your sitemap should include all the URLs to your inventory detail pages. This will allow search engines to spider your inventory detail pages which will help with your SEO on long tail search key phrases.
If setup properly, your website should have a robots.txt file with a reference in it to your sitemap file. This will allow ALL the search engines to automatically discover your sitemap and process it.
Here is an example:
Notice this line in the file:
The sad part is, VERY FEW website providers provide a robots file and dynamic XML sitemap!
Check with your website provider to make sure you have a dynamic XML sitemap.
Chief Technical Officer