Different passwords are used to manage different aspects of your account. You can set them all to be the same, but they are not the same by default.

Billing password

You will generally use your billing password, for viewing invoices, submitting support tickets, etc. at https://account.eppihosting.com/

Webmin/site management password

You will generally use your Webmin/site management password, for editing or uploading files on your website, managing databases, etc. at https://my.eppihosting.com:10400/

Email password

If you set up an email account (e.g., info@example.com) you will typically use this in your email client (e.g., Thunderbird or Outlook or Mac Mail)