Wildcard subdomains allow users of a domain-based WordPress multisite network to create new sites on demand. In this type of network each new site has its own subdomain, and the wildcard configuration means that those subdomains do not have to be configured individually. A wildcard subdomain may also be useful if you're interested in setting up a Wildcard SSL.
To create a wildcard subdomain:
Log into your cPanel account
In the Domains section, click Subdomains
In the Create a Subdomain section type '*' (asterisk without the single quotes)
Note: by putting an asterisk, you'll be creating '*.yourURL.com'), your wildcard subdomain.
From the next dropdown menu choose the domain you want to be the parent of your new subdomain (if you have more than one domain in your cPanel account)
- Enter the home directory for the subdomain in the Document Root text box
Note: this directory will be where files that pertain to the subdomain will be placed. You'll want to point it to the same folder location that your 'wp-config.php' file is located.
Click the Create button