An autoresponder sends an automatic response to anyone who emails a specfied email address. This is often used as an automated out of office reply.
If you want to receive a copy of the incoming email as well as sending an automated response, make sure the email address actually exists in cPanel or is listed as a Forwarder to another email address in cPanel Forwarders.
You can setup an Autoresponder via the Autoresponders tab in cPanel.
An email forwarder forwards an email sent to a specific address on your domain to any other email address you specify.
You can collect all your emails in one email account, yet have many email addresses people can email such as firstname.lastname@example.org, email@example.com etc, all of which you can Forward to your email account. Forwarding is also useful when you want more than one member of staff to receive copies of incoming emails.
You can setup a Forwarder via the Forwarders tab in cPanel.
cPanel provides detailed documentation via a link on the page.