Subdomains are a way of creating separate accounts within your master account, which are accessed as separate URLs. For example, you could set up a “timber” subdomain on your master account “hardware.com”, which would be accessed as “timber.hardware.com”. A lot of larger businesses use subdomains to establish branding and focus on separate product lines, because a subdomain creates a separate URL and web presence.
In practice, a subdomain is a sub folder within the public_html level of your account that has its own cgi-bin directory. The “timber” example above creates a new top-level folder called timber, with a cgi-bin sub-folder. Upload your files for the subdomain to this location, including a separate home file (such as index.htm).
You can create email accounts with the subdomain extension. So you can create an email account called “[email protected]”