Should this:

person1@example.com person
person1 person1@realemail.com
person2@example.com person
person2 person2@realemail.com

be:

person1@example.com person1
person1 person1@realemail.com
person2@example.com person2
person2 person2@realemail.com

? The manpage isn't very specific

This is the only tutorial on the bloody internet that has really allowed me to create email forwarding on a CENTOS VPS and it's working like a treat.

Thank you so much

person1@example.com person
person1 person1@realemail.com

what are `person` and `person1` above? what is the significance of left/right positions above?

This really needs more explanation. I'm not sure which of the main.cf settings in the sample of this post relate to actually forwarding email to an external address, and I'm not sure what the etc/postfix/virtual settings are actually doing in the example.