Google Domains is a domain registration service offered by Google which publicly launched in the United States on January 13, 2015 as per Wikipedia
A search result for ‘domains’ puts Domains.Google.com at the top in a special featured snippet block followed by domain.com. Godaddy and Namecheap are on 3rd and 4th spot respectively. For search of keyword ‘domain name’ which has more than 100,000 monthly searches, register.com is coming first.
The .com price is set at $12 but currently only few countries like USA, UK, India, Canada and some other country users with local biling address are allowed registration of domain names.
The domain GoogleDomains.com forwards to Domains.Google.com and here is what you get with every domain:
Private registration at no additional cost
Easy integration with top website builders
Custom email with G Suite
New domain name endings
Fast, secure, and reliable Internet infrastructure with Google
Simple domain management tools
As a domain registrar Google has branded itself in this space using the generic keyword ‘Domains’ and like most of his other brands, users are taken to a subdomain followed by Google.com. A better option would have been in sticking with a top level domain like its YouTube.com. You will not reach Youtube if you type in the url Youtube.Google.com
If you like to go through the list of subdomains operated by Google here is an answer from Quora.com