Hi, there is the Help tab on the top right where you can find some explanation about available options. There is sais:
SERVER
WordPress
The default sitemap server is light-weight, effective and compatible with most installations. But it is also limited. The XML Sitemaps & Google News plugin adds some essential features and options to the default sitemap generator but if these are not enough, try the plugin sitemap server.
Plugin
The plugin sitemap server generates the sitemap in a different way, allowing some additional features and configuration options. However, it is not guaranteed to be compatible with your specific WordPress installation.
DEACTIVATE
By default, all public content types, taxonomy archives and author archives are included in the XML Sitemap index. If you wish to exclude any content or archive types, you can disable them here.
Select Taxonomies here to exclude then all taxonomy archives from the sitemap index. To exclude only a particular taxonomy, please go to the Taxonomies tab.
Select Authors here to exclude all author archives from the sitemap index. To exclude only a particular author or user group, please go to the Authors tab.