Subdomains are extensions of your domain name. For example, if your domain name is example.com with FastComet you can have unlimited subdomains such as name.example.com, name2.domain.com, name3.example.com and etc.
Subdomains allows you to create a separate address for additional resources of your website with stand alone document directory under which you can have completely stand alone website.
To create a subdomain, login your cPanel and scroll to the Domains section where you will see the Subdomains icon.
Via the Subdomains page you can create a subdomain with a custom name and set the directory name to which your subdomain will be pointed.
To complete the subdomain creation process, please click on the Create button. To have your files or new website accessible via the newly create subdomain simply upload them under the subdomain document root folder of your account.