We are now about 2 years from the launch of the PLATO mission, whose primary aim is the detection and precise characterization of terrestrial planets in the habitable zones (HZs) of solar- like stars. It seems like an opportune time to review our knowledge of planets and how they arrive and evolve in their host HZ, as well as the stellar properties and stellar physics that influence the HZ itself. This objective also offers a valuable opportunity to revisit and refine our definition of the Habitable Zone and the conditions that make planets habitable. As part of this, we would like to assess what the likely impact of PLATO on our knowledge of HZ systems will be.