Astrophysical neutrinos are a unique and powerful messenger for exploring the high-energy universe, allowing us to study regions otherwise inaccessible with astrophysical messengers such as photons and cosmic rays. At TeV to PeV energies, the astrophysical neutrino flux is well-measured, and IceCube collaboration has identified two candidate neutrino point sources (TXS 0506+056 and NGC 1068), as well as neutrino emission from the galactic plane. At higher energies (>PeV) the neutrino spectrum has remained largely unexplored, though a flux of ultra-high energy neutrinos originating from interactions between cosmic rays and the CMB is expected to be observable. This talk will discuss recent efforts within the IceCube collaboration to further characterize the sources of the observed TeV to PeV astrophysical neutrino flux, as well as future plans to study the ultra-high energy (>PeV) neutrino flux with the upcoming balloon-borne PUEO experiment.