  There has been a recent stimulus in the study of alternative theories of
gravity lately, mostly triggered from combined motivation coming from
cosmology/astrophysics and high energy physics. Among the proposed theories,
one that has attracted much attention is f(R) gravity. It is certainly
debatable whether such a simplistic modification of General Relativity can
constitute a viable alternative theory of gravitation. However, it is quite
straightforward to see the merits of such a theory when viewed as a toy theory
whose role is to help us understand the implications and difficulties of
beyond-Einstein gravity. Under this perspective, I review some of the main
lessons we seem to have learned from the study of f(R) gravity in the recent
past.
