Hi,
[ Instead of "&partner_id=2" you could have "&aff=42" ] does not means that you have to add it like that.
I agree that the explanation is not perfect but it explains that you can use another name of the url parameter.
The option allow you to choose the "key" for the parameter, not having "partner_id" but have something else.
For the rest, it is a url parameter, also called "Query String".
en.wikipedia.org/wiki/Query_string
I updated the documentation to avoid misunderstandings.
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.