If you have several domain names and they all point to one website you can set them up so you can easily track which domains are being used to get to your website. This is helpful if you use different domains for different advertisements and/or marketing... or are just interested in knowing which domain names are being used.
First, when pointing domains to a single website I don't use the "A" records (DNS settings) to forward my pointer domains. I simply use the free URL forwarding service that comes with most domain purchases. I know with GoDaddy and DirectNIC URL forwarding is free... and is probably free (or very low cost) with most other registrars too.
The advantage is that by using the URL forwarding service... you can use your site statistics on the main website and see the "Top Referrers" and it will show all the domains that are sending you the traffic.
For example, my main site is www.ROATCorp.com and I have a bunch of other domains like www.RonOfAllTrades.com, www.ROAT.com and .biz, .info, and so forth all pointing to that one main site. I can run my site stats at any time and see which domain is being used to hit my site.
So, if you have multiple domain names, consider using them to point to your main website using the free URL forward service that probably came free with your domain registration. It is a great way to tell if your domain names are generating traffic for you.
Let me know if I can help! Ron