With your IDX Broker account you have two types of sitemaps available for your site. Your Sitemaps are created automatically by the IDX system to include categorized links that lead to all of the active listings from your MLS. This means potentially hundreds or thousands of indexed property details pages.
What is sitemap protocol?
Sitemap protocol is a standard used by programmers to tell search engine crawlers how to find relevant information for indexing. Sitemap protocol was started by Google, but most major search engines such as Yahoo and Bing use this as well. A sitemap is actually an XML file that lists URLs for a site, along with additional metadata about each URL so that search engines can more easily crawl the site.
HTML sitemap
HTML sitemaps are usually a single page, very simple in appearance, and generally only list links. From an SEO perspective, as the search engine crawls your site indexing pages, it may locate some of the pages on your site easier using this sitemap, rather than through the main navigation. People can also use HTML sitemaps to find deeper content that site navigation and site search has failed to provide. Therefore, sitemaps can benefit your site visitors and even play a role in enhancing your exposure on the web. The traditional placement of the link to a Sitemap is somewhere in the footer of the website. You can find your Sitemap in your IDX Control Panel under Design -> Website -> Page Templates.
XML sitemap
XML sitemaps are created specifically for the search engines. The most popular search engines including Google and Yahoo use XML sitemaps as part of the process for indexing the pages on a website. A well-built XML sitemap will tell the search engine what pages are in your site, when they were last modified, and how often those pages are being updated with fresh content. While an XML sitemap is not strictly required, in the last couple of years it has become best practice to submit an XML sitemap in Google Webmaster tools. The XML file supplied by IDX Broker makes it easier for search engines to find all of the pages on your website. The HTML sitemap will automatically be crawled by search engines, but IDX Broker also offers an option for an XML sitemap that can be submitted manually to search engines. This helps the search engines to be more efficient by telling them which pages to visit more often.
To locate the XML file, right click on the text link and "save link as" a file on your local computer to get the file to submit to Google. An XML sitemap is no substitute for good links on your site and a well-defined structure, but it's another tool in your belt that IDX Broker provides to get you more business.
The easiest way to explain the difference between the two sitemaps is the XML sitemap is designed for search engines while the HTML is used by humans. Should you have both available? Yes. Matt Cutts from Google says in this video “once you make an HTML sitemap, making an XML version is extremely easy. So, my advice, do both if possible.”