Observations over the last two and half decades have persuaded cosmologists that (as yet only indirectly detected) dark energy is by far the main component of the energy budget of the current universe. I review a few simple dark energy models, including the currently-standard ΛCDM cosmological model, and compare their predictions to observational data, to derive cosmological parameter constraints and to study consistency of different data sets. I summarize observational constraints on dark energy dynamics and spatial curvature, two parameters that extend away from the time-independent cosmological constant dark energy and flat spatial hypersurfaces of the standard ΛCDM model. I also summarize observational constraints on the Hubble constant. I conclude with a list of my favorite open cosmological questions.