While Google itself isn't offering any website building tools, they've partnered with several website building companies, including Squarespace, Wix, Weebly, and Shopify, in order to provide full services for domain buying customers.
One of the big selling points with Google Domains is that they aren't charging an extra fee for private registration, something that often costs just as much as the domain registration itself with other registrars. Users with their domains registered through Google Domains also get up to 100 email addresses and custom subdomains.
Domain registration is only $12 per year, which makes it slightly cheaper than GoDaddy's rate, however with domain privacy free through Google Domains, it makes it significantly cheaper than GoDaddy's $20.98 for both registration and regular privacy of a .com domain name.
Users currently need a special invitation code to either buy or transfer domains through Google Domains. Google said they hope to make it "more widely available soon" and that they are using the early invite-only beta to work out any issues (e.g., customer support, services) that arise.
While this is Google's first domain registration service offering, Google has actually been a domain registrar since 2005.