  This is a review of some elementary properties of Dirac, Weyl and Majorana
spinors in 4d. We focus in particular on the differences between massless Dirac
and Majorana fermions, on one side, and Weyl fermions, on the other. We review
in detail the definition of their effective actions, when coupled to (vector
and axial) gauge fields, and revisit the corresponding anomalies using the
Feynman diagram method with different regularizations. Among various well known
results we stress in particular the regularization independence in perturbative
approaches, while not all the regularizations fit the non-perturbative ones. As
for anomalies, we highlight in particular one perhaps not so well known
feature: the rigid relation between chiral and trace anomalies.
