Before you set a page to go live you can preview how it is going to look on the live site first.
After creating a page and adding all the appropriate content 'save' the page down, and then in the right hand actions panel select 'preview page' this will bring up, in a new browser window, a preview of how the page will look on the live site.
From this if you are happy with the layout etc you can select the page to go live, if you still need to make changes to the page you can do so by selecting 'modify page'. None of these amends or changes will be seen from the front end until you have selected the page to go live.
In the left hand panel you will see two menus, 'view dev site' and 'view live site'. These menus make it easier for you to view either site and any changes you are making to either sites, without having to open a new web browser window and typing in the web address.
The dev site, is where all of your development happens and where you can work on the site without any changes being visible to the public, content can also sit here ready for when you want to make it go live.
The live site, is the site that is live on the internet for all the public to see - All pages and menus must be ticked 'live' for them to be visible.