Most people have heard they need a sitemap so Google will like their site but what are they and how do you go about creating one?
Sitemaps are recommended for search engine optimization to help Google (and other search engines) discover all of the content on your site. Search engines typically discover the content on your site by following all the links that exist to your site, and within your site (your navigation etc). When you have a large site or one that has a complex structure which might make it harder for Google to find all the pages on your site, a sitemap is especially helpful because it simply lists all of the available content.
Sitemaps come in two flavours: XML and HTML
XML sitemaps are designed for search engine bots, not humans.
HTML sitemaps are more geared toward humans, but search engine bots can crawl them too.