The Friends and Family rate is intended to be offered to travellers who are "friend and family members" of a Carlson employee. That could be a hotel employee, a travel agent (Carlson Wagonlit) or restaurant employee (TGIF) (TGIF sold to Sentinel Capital Partners as of July 2014).

When you book the rate, you are supposed to have the basic data on your friend available at check-in for the hotel to verify that you are indeed authorized to use that rate. Generally, if they ask, they ask for:
1) Employee Name
2) Work location

Please consider that, as per T&C, only employee name and location can be requested only at the check in time.

The new code is RHGRFNF
NOTE:
Booking a rate that you're not entitled to book may result in rate adjustments and Club Carlson account freezing.

In general, the rate is €80 per night in Europe.

*These stays post as "Ineligible" - non-qualifying, non-stay, non-points earning ... so, in sum, don't associate a F&F reservation with your Gold Points account, unless elite perks you hope to enjoy are worth the risk.