Website content — pages, menus, blog posts, header and footer regions, and each site's brand identity — all lives here.
Two versions of every page
A page holds two things at once: the draft you edit in the Studio, and the published version a visitor sees.
Saving only changes the draft. Until you publish, the live site is untouched. Publishing takes a snapshot of the current draft and makes that the live version.
The practical consequence is that you can safely leave a published page half-edited — nobody sees it until you publish.
Scheduling
A page with a publish date in the future does not count as published until that moment arrives. If you have "published" a page and it is not on the site, check its publish date first.
Everything belongs to a site
Pages, menus, blog posts and brand identity each belong to one specific site. A page's slug is unique within that site only — two sites can both have an about page without clashing.
If you cannot find a page you created, the active site at the top of the screen is usually not the one you assumed.
What the Studio edits
A page body is a tree of elements, not a block of text. The Studio edits that tree, and the rendered page is built from it — which is why layout can change without touching code.
Headers and footers are stored separately from pages: edit once, and every page on that site follows.