The breadth of stellar behavior unveiled in recent years, thanks in part to high precision Doppler surveys and space-based transiting exoplanet surveys, has given us new insights into and enabled novel studies of stellar variability, stellar structure and evolution. Here, we discuss how these variations enable us to more accurately measure the physical properties of Sun-like stars, to understand the nature of surface convection and its connection to magnetic activity, and to better determine the properties of planets around cool stars. We show how we may now measure stellar granulation from space-based light curves and use this to obtain a simple measurement of the stellar surface gravity with a precision of ~0.1 dex. We use this, together and solely with two other simple ways of characterizing the stellar photometric variations, to construct an evolutionary diagram for Sun-like stars from the Main Sequence on towards the red giant branch. We expand on this and show how we may use these light curves to measure other fundamental stellar properties and also predict which stars exhibit low levels of stellar radial velocity variability (“RV jitter”), enabling prioritization of transiting exoplanet candidates and facilitating target selection for RV surveys in general. Finally, we highlight previously under- appreciated but relevant astrophysics apparent at current benchmark levels of RV precision from our analysis of precise RVs obtained with Keck HIRES, astrophysics that may become increasingly important as the community pushes to ever higher levels of RV precision.