  Metric-affine theories in which the gravity Lagrangian is built using
(projectively invariant) contractions of the Ricci tensor with itself and with
the metric (Ricci-Based Gravity theories, or RBGs for short) are reviewed. The
goal is to provide a contextualized and coherent presentation of some recent
results. In particular, we focus on the correspondence that exists between the
field equations of these theories and those of general relativity, and comment
on how this can be used to build new solutions of physical interest. We also
discuss the formalism of junction conditions in the $f(R)$ case, and provide a
brief summary on current experimental and observational bounds on model
parameters.
