How do I know my domain?

You can quickly check whether your computer is part of a domain or not. Open the Control Panel, click the System and Security category, and click System. Look under “Computer name, domain and workgroup settings” here. If you see “Domain”: followed by the name of a domain, your computer is joined to a domain.

For More Information Please Refer: https://www.howtogeek.com/194069/what-is-a-windows-domain-and-how-does-it-affect-my-pc/