Using a mygbiz.com domain
When you sign up for a Google Cloud product, we make its applications available for users who belong to an Internet domain that you specify. You can sign up with Google using the domain where you already do business, purchase a new domain, or use a trial domain that Google provides for you. If you choose to use a trial domain, the domain name has the form custom_name.mygbiz.com.
The advantage of using a mygbiz.com domain is that you can try Google products without affecting your business domain, or without purchasing a new domain if you don't have one. You can use your mygbiz.com domain for as long as you like. Eventually, though, you're likely to want to upgrade your Google account to a custom domain that you own. Using a custom domain gives your users email addresses that are more closely aligned with your company brand. Also, certain advanced options are available only with a custom domain; for example, the ability to create custom URLs for users to access Google services or to associate additional domains with your account.