A XML sitemap is a sitemap you make for your website or blog makes it easier for Search Engine crawler bots like Googlebot to crawl your website links.
A Sitemap also tells search engine when a page was updated, does the page’s content change much, and how important a page is compared to the rest of the pages on a website or blog.
A sitemap is basicly a page which list all the links to pages and posts on a website or blog.
A websites XML Sitemap is used by  Google, Yahoo!, Microsoft, Ask, and possibly other search engines to help crawl your site faster for new content by providing tips to web crawlers to crawl your site better.
I have been using WordPress XML Sitemap Generator Plug-in to help me automatically build and update this blog’s sitemap when I make a new post. It is very easy to use and install. All I have to do is install the plug-in and enable it, and it works automatically. You can fine tune the settings for your needs, but the normal settings should be good enough for mosts bloggers needs.
The XML sitemap for your blog can technically be used by humans to browse your website if they visit your example.com/sitemap.xml page, but it lacks navigation and formating, so navigating it can be hard, time consuming, and frustrating if the link names are not descriptive or using the default permalink settings in wordpress like “wordpress/?p=123” instead of the permalink types which list your title like “wordpress/2010/09/14/sample-post/”.
XML Sitemap Generator also notifies/ping Google, Bing, and Ask by default everytime your sitemap is generated because you have updated your blog with new content. However with Yahoo, you need a Yahoo App ID to tell Yahoo your site have been generated.
WordPress XML Sitemap Plugin can help you get more blog traffic from search results pages  by making it easier for Search Engine Crawlers to crawl your website’s pages, so it increases the chance of getting your pages and posts indexed faster.
XML Sitemap Generator also Compresses your XML with Gzip compressi0n, so it takes up less space on your web server, and can be loaded faster when both humans and search engine crawlers use it.
You can also rebuild your sitemap manually if you change something on your server, but in my experience, I never used this feature since I hardly make changes to my server.
There is also a debug function in XML sitemap generator, but I never used it since the XML sitemap generator plug-in works great everytime I use it.
The default settings should be fine for most of your need, but you can also tell XML sitemap generator to include tags, categories, and archives. But, I don’t recommend including tags, categories, and archives since it will make your sitemap size bigger if you have a lot of tags, categories and archives in your blog, so it will make it longer for Search Engine Crawlers to load and crawl your sitemap, and it is best to showcase your best content like your posts, and pages in my opinion.
A sitemap improves the chance of your site getting crawled by Search Engine Crawler bot, but your pages still might not get indexed if the content is not good, etc. It is also important to make sure your website has an HTML sitemap which list your categories, and pages, but do not name your HTML sitemp with a none descriptice name like sitemap since sitemap is not a common word in the english dictionary. “website-map” is a more descriptive and simpler name for your HTML sitemap for humans to use to better navigate your site. An HTML sitemap may also help other search engines which don’t use the XML sitemap format to index your links.
For more Information about XML Sitemap Generator visit: arnebrachhold.de/projects/wordpress-plugins/google-xml-sitemaps-generator
The XML Sitemap Generator plugin is a must-have plugin for any serious blogger. In fact, I have it installed on the first day when my blog was brought live!
I agree the XML sitemap is a must-have plug-in for serious bloggers since it helps search engines like Google crawl your articles easier.
Are you interested in possibly reviewing/comparing general sitemap generator tools?
@Thomas sure if it is a plug-in for WordPress.
I’m so glad that you decided to write this article about XML sitemap generator plugins. You can never discover too many ways to try and get more traffic to your website and increase it’s ranking.