Packages "fai-nfsroot" + "fai-setup-storage": when do I need to install them?

[c.monty at web.de]

Hello!

I installed FAI from official repository executing 
aptitude install fai-quickstart

After the installation I can see that some packages are not installed:
fai-nfsroot
fai-setup-storage

In which scenario do I need these packages?
And how should I install them in case they are required?
The installation in faiserver returns this error:
ERROR: The package fai-nfsroot can only be installed inside the nfsroot.

THX