[TYPO3-english] What is Typoscript and why has a page load failed?

[James Moe]

opensuse 42.2
linux v4.1.36-41-default x86_64
typo3 v7.6.10

I am just starting with Typo3. I created a Home page. I viewed it. This is the result:

Service Unavailable (503)
No TypoScript template found!
More information regarding this error might be available online.

What is a Typoscript template?
How do I create a Typoscript template?

If a Typoscript template is needed to view a page, why was it not included in the construction?