What is upgrading?
All Tank sites kick off on the 'withtank.com' domain on a subdomain of their own. In other words your new site starts off on a domain like 'yournewsite.withtank.com'. This URL is the address at which this site is immediately accessible to everyone on the Internet, and you can share the address with anyone at this stage.
Understanding domains, sub-domains, URLs and web addresses
Before we continue, some terminology to help you understand certain aspects better:
'withtank.com' is a domain, which in turn is a subdomain of the 'com' top-level domain (TLD). 'yoursite.withtank.com' is a subdomain of the 'withtank.com' domain - in other words it is part of a larger domain 'withtank.com'.
Subdomains are sometimes referred to as 'vanity domains'. Taking things further 'http://yoursite.withtank.com' is an URL or web address viewable or accessible through a web browser.
If you take some time to understand these concepts and learn the terminology you'll appreciate it further down the road - it's becoming commonplace vernacular nowadays and might even come in handy at the dinner-table.
It's a simple process, really
At some stage you might want to access your site at your own domain (instead of a subdomain on the withtank.com domain), and we call this process upgrading. It is relatively simple from a technical point: we map either a new domain or an existing domain to the Tank server, and we make a small change or two to your site to 'catch' this domain, and your site (and all the content you added) now lives at yourowndomain.com. The older subdomain address is still valid as you might've emailed or bookmarked that by now.