Publishing the website means sharing all the changes in the site to the viewers. To publish the site, click the Publish button at the top-right side of the editor.
It will open a window for customizing the web address and privacy of the site.
Note: After publishing the site, you can still edit it. However, if you want the viewers to see the recent changes, you need to click the publish button again.
If you have other questions, feel free to message me via Google Chat.