A landing page is an enhanced page used for a section's home page or a portal site. The landing page has its own content (i.e., Section, Title, URL slug, Video or Image, Heading, Body and Button fields), but it also references several different content types that exist outside the landing page itself (i.e., slideshows, calls to action and infographics).
The landing page also includes a news and events feed concept under the "Manage queues" and "Settings" options in the administration bar. This allows published news articles and events to be feed into the landing page—regardless of which section originally created them.
See examples of landing pages in action: