This is the events page. It lists all previous and upcoming events on your site. The Legumeinfo Jekyll theme does not provide an events page since not every site may want such a page, but an events layout is provided so sites that want an events page don't necessarily have to implement one from scratch.
The events listed on this page are Jekyll posts. When the site is built a separate page is generated for each post. An event layout is provided by the Legumeinfo Jekyll theme for these generated pages.
The events card on the right side of this page is not actually specific to this page. The Legumeinfo Jekyll theme supports adding this card to any page via YAML front matter.
Note that future post must be enabled to support listing upcoming events.