They are an additional tool to help the search engines when they crawl a site. There is no requirement for any sitemap and your pages will get indexed without them if you pay close attention to navigation within your site.
That's right but imagine if the SEs crawls the sitemap. Do you think it will be easier to crawl those links on your sitemap rather than crawling the entire site without one (sitemap)? What do you think mate?
Google Webmaster Tools specifically has a place for you to list and submit your sitemap.xml If they go to the trouble of encouraging the xml sitemaps, it's a safe bet to assume they look favorably on them. It takes so little effort to create and submit an xml sitemap, why would anyone not want to do it?
XML site-map is really help your site in better site indexing, and as seo point of view it is a recommended activity. Do attention in your navigation but i suggest that also go for site-map as well.
Site map is the only page where you can put all pages of your website together, and it will easily crawl by Google.
SiteMap is used for Navigation in a website. There are two types of Sitemap: HTML and XML. HTML sitemap is used by the visitors visiting the website and XML sitemap is used by the crawlers crawling the website... both websites play a very important role in indexing and must be included in a website and updated regularly...
XML sitemap is helpful for the search engine to crawl your website as sitemap contains all pages url.
Even though I use sitemaps for all of my sites, I think that they are a waste of time. Some of my sitemaps have nearly every link submitted indexed, while some sitemaps have only a handful of links indexed. I suppose it is randomly selected on how many sitemap links are indexed.
this will works for small sites but for large sites that have dynamic content, it will be necessary to build sitemap