Beside the name or word, Domain has extension after the word. It called by extension which are comprise of 2 types:

1. Top Level Domain (TLD) such as .Com, .Net, .Org, .Edu, .Biz or . Info
2. Country Code Top Level Domain (ccTLD) such as: .Co.Uk (commercial domain for UK), .De(commercial domain for Germany) etc.

Now, this is very interesting part! We can only find 1 unique domain name in all the places of the world. In Other word, If a domain name already used by someone, no body in the world can  use it until it is expired and the person is not extend the domain. With this principle, you will know that if we have a good domain name, you can have a good business opportunity such as sell domain to some one who interested and needed the domain name.

I will give you some example that I get from www.DNjournal.com for good value domains :

1. Sex.com was sold in Jan. 2006 but the exact price was not disclosed. CNN.com said sources indicated a cash and stock package worth approx. $12 million was paid for the domain.
2. Diamond.com was sold at Pvt Sale for $ 7,500,000 on May 19, 2006
3. Vodka.com was sold at Sedo for $ 3,000,000 on December 19, 2006
4. Computer.com was sold at Moniker/ T.R.A.F.F.I.C for $ 2,100,000 on November 27, 2007
5. Chinese.com was sold at Sedo for $1,120,008 on July 24, 2007

Actually several method of getting income from domain but I will explain especially for 2 methods:

1. Domain Sales
For purchase another person’s domain or sell our domain name to the market, you need to find the market.
Domain market place normally has 4 services:

- Domain Appraisal
Domain Appraisal is a service for appraise for actual domain worth in market.
- Domain Brokerage
Domain Brokerage is a service that make us enable to hire a broker to appraise our domain and look for the buyer for our domain.
- Domain Escrow
After we have a deal with the buyer, we need one more process that guarantee that transfer for a domain can run safely in technical aspect also in the payment.
- Domain Auction
This service is allowed us to sell domain with auction system.

There are several Big Domain market place such as: Sedo.com , AfterNIC.com, Pool.Com , SnapNames.Com

2. PPC Income
What about if we have domains but we don’t want to sell it? We also can earn money with PPC Income system such as: Parked.com, Fabulous.com, DomainSponsor.com, Sedo.com etc.

The principal of this business is very simple, we only need to provide some empty domains and park to their network and let them manage the content related to your domain name(s), and they will optimize them to display relevant, paid advertising to visitors.  Once the visitors click the advertisement, we can get the payment. All we have to do is sending the visitors to our domains.

Here is some resources for the ones who will start business in Domain :

1. Beginners for Domain business : www.NameNewbie.Com
2. Latest information of Domain Name business : www.DNJournal.com
3. Domain Market Place : www.Sedo.com, www.AfterNIC.com, Pool.Com, SnapNames.com
4. PPC Income : www.Parked.com, www.Fabulous.com, www.DomainSponsor.com, www.Sedo.com
5. Check the domain owner : http://WhoIs.Sc/domainname.com
6. Check the availability of domain name : www.NetCheap.com
7. Domain Forum : www.DNForum.com, www.DomainState.com, www.NamePros.com
8. Pawning a domain : www.DigiPawn.com

There are some Domain parking service provider such as : sedo.com, namedrive.com etc but I prefer to use Parked.com
rather than the other because it is more simple. You simply let them manage the content related to your domain name(s), and they optimize them to display relevant, paid advertising to visitors.  You can see a sample of the page in this link : http://meanwhile.com/?domain=pocketcandy.com
The advertisers pay us for results, and they distribute some of the highest commissions in the industry back to us.
Below some tips that useful for you to subscribe Parked.com :

Let me explain how to start make money with Parked.com :
1. You need to prepare 10 Empty domains before you sign up Parked.com
2. can be .com   .net   .biz  or  .info
3. better take 10 domains with different topics for example : dating tips.com, financial solution.com etc
4. Avoid similar names such as: allaboutpets.com, allaboutdating.com etc. make domain name as natural as possible and get various topics. Don’t use superlative domain names such as : bestaffiliate.com, 1st inFinancialSolution etc
5. Avoid misspelling domain names or similar with big names like ebay, google etc
6. Study keywords carefully and make the targeted keywords as domain names.
7. tips: don’t use free email when you subscribe Parked.com, better you use email from your domain.
8. U need to setup your domain for Whoisguard as non active.

After you setup the domains, the next step is getting traffic to your domains, you can use adwords, overture etc.