The Search Engine Metainfo Dashboard is a table that allows you to set and override with custom and specific metainfo each links contained in the sitemap of your site.
If you open the Search Engine Metainfo Dashboard for the first time or custom metainfo are not specified for any links, it will show empty data and the default ones will be used as set in your Joomla! system, without any override by JSitemap.
The Search Engine Metainfo dashboard allows you to specify exact metadata used by search engines and socials for each link of your site included in the sitemap, without worry about Joomla! menu and routing.
Normally Joomla! renders metainfo based on a complex way of routing elements, the resulting metainfo could be taken by menus, articles, categories, etc. With the Search Engine Metainfo Dashboard of JSitemap you can override exactly and take control of metadata on a link basis, overriding the default Joomla! ones.
If you want to know your current meta title and description used for links by Joomla!, simply open the SEO Spider instead. The SEO Spider always fetch and show the current meta informations from pages, so it's optimal to use the SEO Spider in conjunction with the Metainfo Dashboard. While the SEO Spider shows you the current meta title and description for each page link you can choose to override it with a better one using the Metainfo dashboard.
Starting from JSitemap Pro version 4.1 a new feature allows you to auto populate the Search Engines Metainfo Dashboard fields with all your current values for titles and descriptions as being generated by the standard Joomla! system for categories->menus->articles, etc. Clicking on the button visible in the image below the process will start for links showed in the current page. Notice that it's not strictly required to auto populate all links, if you leave all values unaltered this process is simply redundant and useless. It makes sense to use the Search Engines Metainfo Dashboard to override and improve basic Joomla! titles and descriptions when and if required.