Getting started with the basics of publishing pages and saved versions.
The Publish button is located on your Editors Toolbar and it's used to publish pages live to your visitors. When it goes live the Publish button will change to Live. Until you publish your page, your visitors can not see the latest changes you have made to that page. Publishing pages works per page, so any changes you make to other pages you need to also press the Publish button on those pages to make those changes live.
Every time you publish a page, a saved copy is stored and you access it on the Editors Toolbar by selecting the Saved Versions option. Page Versions contains changes to each page your on and you need to be on that page to see the list of versions per page. Header & Footer Versions does as it says, applying only to the Headers and Footers of your website (this applies to all pages).
In the Versions List, you will see dates, details of who published the page and options to use a previous version or delete it. You can go backwards or forwards of different saved versions of each page any time.