[en] The causal set program is one of a number of discrete spacetime approaches to the problem of quantum gravity. It proposes that the microstructure of spacetime is that of a partially ordered set, a causal set, in which the partial order encodes information about the causal structure of spacetime. Herein, I will introduce the main hypothesis of this program and discuss some of the developments that have taken place over its approximate 20-year history. This semi-technical paper is intended for general physics students and specialists in other areas of physics