Below you can see a quote from the CPanel itself, which best summarizes what a subdomain is and what it’s used for.
A subdomain is a subsection of your website that can exist as a new website without a new domain name. Use subdomains to create memorable URLs for different content areas of your site. For example, you can create a subdomain for your blog that is accessible through blog.example.com and www.example.com/blog
How can I add and manage subdomains?
As you open your CPanel you’ll see a link to subdomains. See the image below.
Next you’ll come to a page where you can add and change subdomains. Keep in mind, when changing subdomains, you’ll still have to change the links to these subdomains on your website, otherwise, if people click on these links, they’ll see a 404 page.
Can I always add new subdomains?
Yes, this is no problem at all and it brings no extra costs to the hosting plan you have. Adding subdomains is completely free, so add as many as you like!