Project talk:Sandbox

How is the Sandbox page created?
I would like to know how the sandbox page on mediawiki.com was createzejfoeifoejfafadflajdkfjfjlaldjfkjdsajfjdlkjfalsjdfopwj[jgirhjbonved. Is there a template that is being used? I would like to modify the sandbox on the mediawiki I work on so it is similar to this one. Thank you.