A domain alias is a domain name that can be used as an alternate name for another domain
Creating a Domain Alias is creating additional Domain Names that would point to the IP of a different domain. The only difference is that the Domain Alias has no files (web pages) of its own. Instead it uses the files of the aliased domain name. BORING!
Let’s think of it in superhero terms! Superman has the alias of Clark Kent, Spider-Man is Peter Parker, The Hulk is Bruce Banner. The Hero name and alias refer to the same person, but their second identity doesn’t use any super powers, they are just a vessel to the good stuff! Superman is your main website address of let’s say www.youhavesuperpowers.COM which has all of your content and superpowers on it. His alias Clark Kent, would be your Domain Alias of let’s say www.youhavesuperpowers.NET, this address doesn’t have any content or use any super powers, it’s just an address that leads to the main website address.
Now when someone types in www.youhavesuperpowers.NET, it will redirect them to the .COM webpage, kind of like when Clark Kent finds a person in distress, he finds a telephone booth and becomes Superman!