Sitemaps basics

Sitemap is a special page on a website that contains information for the accessible pages of a website. Sitemaps help visitors and search bots to find pages. The sitemap is important for SEO of a site because it ensures that all desired pages can be crawled. Even if your website navigation uses JavaScript, your pages will be crawled if they are correctly described in your sitemap.
Sitemaps are very helpful if you have pages on your website that aren’t discovered by the search engines.

Sitemap formats

XML
The most widely used sitemap format is XML. Google first started to use sitemaps in 2005 and later most of the big search engines announced support for the protocol.
The XML sitemap format is relatively simple. The document must consist of these XML tags:

• urlset – the base tag. All other tags must be parts of this one.
• url – the base url tag
• loc – the full url of the page
• priority – the priority of the page relevant to other pages of the site
• changefreq – How frequent the page changes
• lastmod – last modified

Feeds
Site feeds can be used as sitemaps in most of the search engines. In fact Google uses the site feeds to crawl blogs hosted on blogger. This method has some drawbacks but in most of the cases it is pretty convenient.

Text file
You can use a text file for your sitemap. It can be any extension you like but the best way is as a .txt file.

Submitting Sitemaps
Most of the search engines offer a way for webmasters to submit their sitemaps. For Google you can use Google Webmaster Tools to submit your sitemap.