This feature allows remote hosts (servers) to access MySQL® databases on your account. This is useful, for example, if you wish to allow shopping cart or guestbook applications on other servers to access your databases.
Identify the Remote MySQL option in the CPanel.
Allow a remote server to access your databases
To specify remote hosts that can access MySQL databases on your account, perform the following steps:
Enter the host’s name or IP address in the Host text box.
You may enter a fully qualified domain name (FQDN) or an IP address.
You may use the percentage sign character (%) as a wildcard. For example, to allow access from all IP addresses that begin with 192.68.0, enter 192.68.0.%.
Click Add Host.
Deny a remote server access to your databases
To deny database access to a remote host, perform the following steps:
1) Click Delete next to the host’s name or IP address.
2) Click Yes.
Read more about remote mysql database option at official documentation here: https://go.cpanel.net/RemoteMySql