For instance, you may actively use mydomain.com, and have mydomain.org registered but doing nothing. Here's how you can use the .org as a parked domain redirecting to mydomain.com, benefitting from the extra traffic.
Having bought and registered the domain with your registrar, head to your VPS' DNS manager & add the new domain's settings, like this.
Make Your Domains Work for You, Not Your Registrar
When you register a new domain, often it'll be auto-parked by your registrar, until you do something with it.
This will benefit your registrar, because any search traffic the domain gains will filter there and, if they've strapped on any adverts, they'll get the click thru' payment, not you.
And if you officially park the domain with the registrar, with most, it's the same deal .. they get the kickbacks, or at best maybe you'll be offered a cut.
So. Take control of those spare domains. You bought them. For the sake of 10 minutes setup, why give the benefit to someone else?
.. But. There is one difference to the methods linked directly above, and this is the data we add to the vhost file.
In your terminal, open the vhost file ..
.. and delete the lot, replacing with this (but swapping these two domains for yours) ..
That's a basic rewrite rule and, once your Nameserver and DNS records have propagated, it will redirect any request for mydomain.org or www.mydomain.org to mydomain.com. If you've set up your primary site www.mydomain.com to resolve as mydomain.com, use mydomain.com instead in the rewrite rule.
Er, thassit! So if you've got any spare domains hanging about doing nothing, go get them working for you.