  Andreev bound states are an expression of quantum coherence between particles
and holes in hybrid structures composed of superconducting and
non-superconducting metallic parts. Their spectrum carries important
information on the nature of the pairing, and determines the current in
Josephson devices. Here I give a short review on Andreev bound states in
systems involving superconductors and ferromagnets with strong
spin-polarization. I show how the processes of spin-dependent scattering phase
shifts and of triplet rotation influence Andreev point contact spectra, and
provide a general framework for non-local Andreev phenomena in such structures
in terms of coherence functions. Finally, I demonstrate how the concept of
coherence functions cross-links wave-function and Green-function based
theories, by showing that coherence functions fulfilling the equations of
motion for quasiclassical Green functions can be used to derive a set of
generalised Andreev equations.
