A sub domain is a part of a domain under the DNS hierarchy(Domain Name Service ). It is also called as child domain. Sub-domain are mainly used to organise the website content.The sub-domain  are represented in the format - “sub-domain_name.domain_name”  i.e. the sub domain name and domain name are separated by a period /‘.’  . Example sub1.xyz.com , sub1 is the sub-domain of xyz.com

Use of sub-domain:
  • Sub-domain are used to organize the website content.For example in your domain “xyz.com”  all your photos  can be stored under the sub-domain name photo.xyz.com.
  • It can be also used to share  the given domain space with other users ,this can be done by  providing them subdomains with their own username and their own  password  and also change the feature access for the respective  users.For example admin.xyz.com , emp1.xyz.com  and emp2.xyz.com  
  • We can also use to shorten long links which is easier to access. . For example, the link "http://xyz.com/offers/bonus/profile.asp" can be replaced to the subdomain "profile.xyz.com" Which is easier to access.
 
How to List Sub Domains

Step 1: First login into your WHM panel

Step 2: click on List sub-domains

Step 3: It will display the list of sub-domain of your domain