This is used to verify the authenticity of the https web browser, or mail server or whatever. Without one you get an error saying:
Your connection is not private
Attackers might be trying to steal your information from {SOME IP} (for example, passwords, messages, or credit cards). Learn more
Point of clarification: It's a Domain Certificate and allows a URL the use of HTTPS. It's not really an OWNERSHIP certificate per se, although contact info was used to create it.