This is the tools page. It lists all of the tools in your site. The Legumeinfo Jekyll theme does not provide a tools page since not every site may want such a page, but a tools layout is provided so sites that want a tools page don't necessarily have to implement one from scratch.
The tools listed on this page are loaded from a YAML file. The tools menu on the left is not actually specific to this page. The Legumeinfo Jekyll theme supports adding this menu to any page via YAML front matter.