Sitemap.xml is used by various search engines to better describe your website hierarchy and provide a list of links with additional information about priority and update frequency for every page. Sitemaps can also contain images attached to posts or pages.
Usually, sitemap.xml is a collection of the main index file and multiple sitemap files with links. The usual practice was to create these files and place them in the website root (this is required by search engines). And, this was the way GD Press Tools Pro generated sitemaps, saving XML files. But, this was causing problems with multisite networks where each blog needs own files, and that made impossible to use the plugin for this purpose in networks. Now, GD SEO Toolbox Pro is not saving any XML files, it is building virtual sitemaps and serving them, so it can be used in networks.
The plugin allows you to change the name of the sitemap index file, set number of links per map, auto-notifies Google, Bing, and Yandex when the sitemap is rebuilt, include images for posts and pages. Also, you can control content for the sitemap, priorities, and frequencies for archives, single posts and more. Each post, term, and the user also have meta box for configuring them for sitemap inclusion if you want to go into fine tuning.
To make sitemap readable in browsers, plugin includes XSLT transformation files to render XML as HTML.