  The study of entanglement in systems composed of identical particles raises
interesting challenges with far-reaching implications in both, our fundamental
understanding of the physics of composite quantum systems, and our capability
of exploiting quantum indistinguishability as a resource in quantum information
theory. Impressive theoretical and experimental advances have been made in the
last decades that bring us closer to a deeper comprehension and to a better
control of entanglement. Yet, when it involves composites of indistinguishable
quantum systems, the very meaning of entanglement, and hence its
characterization, still finds controversy and lacks a widely accepted
definition. The aim of the present paper is to introduce, within an accessible
and self-contained exposition, the basic ideas behind one of the approaches
advanced towards the construction of a coherent definition of entanglement in
systems of indistinguishable particles, with focus on fermionic systems. We
also inquire whether the corresponding tools developed for studying
entanglement in identical-fermion systems can be exploited when analysing
correlations in distinguishable-party systems, in which the complete
information of the individual parts is not available. Further, we open the
discussion on the broader problem of constructing a suitable framework that
accommodates entanglement in presence of generalized statistics.
