What IS a sudomain, you say? Well...
Say you have a domain name 'example.com'. A subdomain would look like 'sub.example.com'.
Note: where 'example.com' is your site URL.
The domain name system is a hierarchy of names, and include hostnames and subdomains. For our purposes, there is not much difference between a hostname and a subdomain (there is a technical difference if you're running a network of servers).
Create a New Sub-Domain
To create a new sub-domain:
Log in to your cPanel account and click Subdomains from the Domains section
Enter a new sub-domain, like 'sub.example.com', in the Subdomain blank
Add the document root information in the appropriate blank and click Create
cPanel will create a DNS entry (an A record) for that subdomain pointing to your IP address.
Advanced Uses of Subdomains
C Name Records
If you use a service like Google Apps for Domains then you may need to create a Cname record in DNS to point:
Example: 'start.example.com. CNAME ghs.google.com.
To create a C name record submit a support ticket requesting it and we will take care of it. You would not create a subdomain in cPanel, which creates the A record. Cname records and A records cannot coexist in this manner.
You can delegate a subdomain to another ISP, webhost or network provider. This is not done through the cPanel Subdomains. You would need to submit a support ticket with the remote network's DNS/Nameservers and we will create NS records delegating the subdomain.
Example: you use DynDNS to create a DNS record for your home IP address assigned to you by your DSL provider. If we created a hostname/subdomain for 'home.example.com' and point it to your IP address at home, it would not work when your ISP changes your IP address.
Instead, you would register with DynDNS to update a hostname 'home.example.com' with your IP address every time it changes. In order for this to work, ASO will create a NS record, referring all requests for 'home.example.com' to DynDNS.
home.example.com. NS ns1.mydyndns.org. home.example.com. NS ns2.mydyndns.org.
Ultimately, ASO will answer requests regarding your website, email server, etc., and then for anything related to your home IP address ASO will refer all requests to& DynDNS who then has the necessary information about 'home.example.com'.