Per User Group Specials allows you to offer product discounts to only a specific user or group. Like other Zen Cart specials, these are visible in the catalog prior to checkout.
Zen Cart has a built-in mechanism for discounting individual items called Specials (accessible under Admin->Catalog->Specials).
But Specials are available to all customers, and this may not be what you want. Using this mod, you can segment specials so that they are only available to a particular user or group.
Per User Specials may be accessed from the Admin->Customers->Customers screen.
Per Group Specials may be accessed from the Admin->Customers->Group Pricing screen.
The list of Per User/Group specials is shown on its own screen. Of course it looks similar to the regular Specials screen. It can be directly accessed by going to the Admin->Customers->Per User Group Specials.