Importance of having a domain name:

Whenever you change your web host, your domain can be the same. You'll not lose visitors and page ranks in search engine index. A domain name can also give you website credibility.

What makes a good domain name?

It's good if your domain name is same as name of your website, corporation name, brand name, web content etc. Domain name should have meanings, be easy to remember and type correctly.
About the length of domain name, there appears to be some disagreement about whether a long or short domain name is better. Short domain name is easier for human to remember and less prone to typos, while long domain names that have your site keywords in them have an advantage for search engines robots thus fare better in a number of search engines.

How to register domain name?

Think of the domain names you want to use.
Go to domain registrars and apply for the domain name.
Set the DNS IP address and name server of your host, then after 24/48 hours You can access your website through your domain name.

Domain URL Forwarding

With URL forwarding you can use your domain to direct any visitor to an existing website.
You can add meta tags Title, Keyword and Description for your URL Forwarding.
There are two types of URL Forwarding to choose.
(1) Standard Redirection: sends your domain visitors to any website you specify and show the true address of the destination website (not your domain name )in the viewer's browser.
(2) Stealth Redirection: just like Standard Redirection, but continues show your domain in your visitor's browser when they reach the website and while visiting any page in that website.

"Pass Subdirectories" option : This option allows visitors to enter file names or subdirectories following your domain and be redirected to that subsection of your destination website.
(1)If this option is off, visitor can not access subdirectory files directly.
For the domain: mydomain.com
Destination address set: http://www.exsitingsite.com/user
Visitor enters: http://www.mydoamin.com/file2.html
Visitor CANNOT redirected to: http://www.exsitingsite.com/user/file2.html
(2)If this option is on, visitor can access subdirectory files directly.
For the domain: mydomain.com
Destination address set: http://www.exsitingsite.com/user
Visitor enters: http://www.mydoamin.com/file2.html
Visitor CAN redirected to: http://www.exsitingsite.com/user/file2.html