A domain alias is an additional/alternate domain name created for the primary domain of the website. It is similar to multiple front doors used to reach one location.
With alias domain, you can assign more than one domain name that points to your website. For example, if domain name for your website is example.net, you can register another domain name for the same website - example.com and have it point to the location of example.net.
When you use domain aliases along with a Google services account, you become capable of giving users an email address at multiple domains.
For example, a retailer Ravi who has a domain name – email@example.com can ask his company people to send a mail to alias domain- firstname.lastname@example.org. Mail sent to both the domain addresses will arrive in the same inbox of Ravi.
Domain alias is also called domain stacking or domain name pointer to root.
Benefits of a domain alias:
• It eliminates the need to manage multiple email addresses for a single website.
• With it, you don’t need to create new email addresses.