  Turbulence in a superfluid in the zero temperature limit consists of a
dynamic tangle of quantized vortex filaments. Different types of turbulence are
possible depending on the level of correlations in the orientation of vortex
lines. We provide an overview of turbulence in superfluid $^4$He with a
particular focus on recent experiments probing the decay of turbulence in the
zero temperature regime below 0.5 K. We describe extensive measurements of the
vortex line density during the free decay of different types of turbulence:
ultraquantum and quasiclassical turbulence in both stationary and rotating
containers. The observed decays and the effective dissipation as a function of
temperature are compared with theoretical models and numerical simulations.
