The content of a page, when viewed in a space in which the Enterprise Theme is enabled, is surrounded by sections (muss noch verlinkt werden) such such as the header and footer, the sidebar and the section below the content. Furthermore there are several other elements like the page metadata, buttons to watch, edit, share, etc. By setting the page to be a landing page, you can set the focus on the content.
Landing pages are particularly useful when the page is used as a dashboard (muss noch verlinkt werden).
Keep in mind that by setting a page to be a landing page, you might remove the page tree which is commonly placed in the sidebar. So make sure to provide some sort of navigation option in order to not confuse users visiting that page.