Sub-domain makes your URLs shorter and nicer. It allows you to categorize content of your website. They also help in search engine rankings because they are treated as separate website address by the search engines. However, you should consider few things before settling for sub-domains for your website.
A sub-domain can be used to suggest important subdivisions of your website, such as, functions, services and departments. For example, universities can use sub-domains for major divisions such as social sciences, physical sciences, humanities and so on.
Different ways of using sub-domains:
An online seller can effectively use sub-domain to distinguish between information given on website. The sub-domains can be used to separate company information from forums, webstore and from affiliate programs.
Sub-domains can also be used by businesses to identify individual computer having their unique IP address. In this case, machine names can be used as sub-domain names.
For example: A company has two servers serving two different departments, accounting and marketing. The servers can be identified with two different sub-domain names that signify their departments, such as, accounting[dot]companyname[dot]com and marketing[dot]companyname[dot]com, where companyname is the domain name.
Sub-domains also prove useful for busy sites. Sub-domains can be used to reduce the load time for visitors. Many popular businesses experiencing high traffic use sub-domains for load balancing. For example, a visitor wants to visit a www[dot]busysite[dot]com. The load balancing sends the user to different server that reads as www2[dot]busysite[dot]com or www7[dot]busysite[dot]com.
Sub-domains prove very useful when a website owner wants to organize the information presented on a website. Different sub-domains can be used to present different topics. The use of sub-domains allows the website owner to transfer all the information of a particular topic to a different dedicated computer.
Sub-domains are also useful if you have two different businesses dealing with different sections. A sub-domain can prove adequate for your business purpose. For example; if your business is related to games and education, you can have two sub-domains such as gaming[dot]yoursite[dot]com and education.yoursite[dot]com.
Sub-domains can be created free as long as you own the domain name. There are no restrictions on number of sub domain names you can create. You are also not required to pay any annual fee to registrar the sub-domain names you create.
Sub-domain can also prove useful if you have separate sections in your website with different languages, for example; jp[dot]yoursite[dot]com, and fr[dot]yoursite[dot]com.
Choosing the right domain name is based on your business preferences and personal preferences. You have to decide the sub domain name by yourself by analyzing the content present on the website.