When an element is hidden, be it a page, a content element or a news item, it will not display in the frontend. You can, however, preview it in the backend.
In the Core, and in extensions that follow best practice, all options related to visibility are controlled in the Access tab of the page properties.
You can specify a period of time for content to be visible. This might be useful for seasonal announcements or festive periods. Any page or content element with a defined Publish Date will not be visible before that date. If it has an Expiration Date, it will be hidden from that point onward.
When you set a publication date in the future then try to navigate to that page, you are redirected to the home page.
When you enable the Extend to Subpages setting, the publication date (and other access restrictions) also apply to all child pages of the current page. This makes it possible to apply restrictions to a whole branch of the page tree.