Domain Aliases allows you to assign more than one domain name to one web site
with Action you can have an unlimited number of domains pointing to a single web
site.
For example, if you have the domain "mydomain.com" set up as an
alias to the hosting account for "myotherdomain.com," anyone browsing to
"mydomain.com" will go to the "myotherdomain.com" Web site.
With 301
redirect, the Web browser connects to one Web server hosting "mydomain.com", and
that Web page redirects the browser to another server hosting
"myotherdomain.com".