  Understanding Dirac-like Fermions has become an imperative in modern
condensed matter sciences: all across its research frontier, from graphene to
high T$_c$ superconductors to the topological insulators and beyond, various
electronic systems exhibit properties which can be well described by the Dirac
equation. Such physics is no longer the exclusive domain of quantum field
theories and other esoteric mathematical musings; instead, real physics of real
systems is governed by such equations, and important materials science and
practical implications hinge on our understanding of Dirac particles in two and
three dimensions. While the physics that gives rise to the massless Dirac
Fermions in each of the above mentioned materials is different, the low energy
properties are governed by the same Dirac kinematics. The aim of this article
is to review a selected cross-section of this vast field by highlighting the
generalities, and contrasting the specifics, of several physical systems.
