This project used to be hosted by WorldFamilies.  In May 2018, it was transferred to FTDNA because World Families has closed down.
It is a genetic attempt to bring all who have Jeffries blood in their veins together (no matter where in the world they reside) to ascertain who belongs to which family.
If you look at the DNA results you will see the families that exist in the project.
It is best that men test their Y chromosome as high as they can.  Females, while welcome will do well if they ask their brother or father or a male cousin in their Jeffries family who will act as their proxy.