The circumgalactic medium (CGM; non-ISM gas within a galaxy virial radius) regulates the gas flows that shape the assembly and evolution of galaxies. Owing to vastly improved capabilities in space-based UV spectroscopy with the installation of HST/COS, observations and simulations of the CGM have emerged as the new frontier of galaxy evolution studies. My recent work suggests a rapid cycling of massive amounts of gas on scales of hundreds of kiloparsecs that in turn has raised pressing questions concerning the physical characteristics of the gas in the halos of galaxies. In this talk, I will discuss new constraints we have placed on the origin and fate of this material by studying the gas kinematics, metallicity and ionization state. I will conclude by posing several unanswered questions about the CGM that may be addressed with future survey data and hydrodynamic simulations in a cosmological context.