  The determination of the most appropriate starting point for the theoretical
description of Fe-based materials hosting high temperature superconductivity
remains among the most important unsolved problem in this relatively new field.
Most of the work to date has focused on the pnictides, with LaFeAsO, BaFe2As2
and LiFeAs being representative parent compounds of three families known as
1111, 122 and 111, respectively. This Topic Review examines recent progress in
this area, with particular emphasis on the implication of experimental data
which have provided evidence for the presence of electron itinerancy and the
detection of local spin moments. In light of the results presented, the
necessity of a theoretical framework contemplating the presence and the
interplay between itinerant electrons and large spin moments is discussed. It
is argued that the physics at the heart of the macroscopic properties of
pnictides Fe-based high temperature superconductors appears to be far more
complex and interesting than initially predicted.
