The relativistic wind from a newly formed pulsar creates a bubble of magnetic field and relativistic particles in the surrounding supernova gas. The evolution of the pulsar nebula depends on the properties of the supernova and its interaction with the interstellar medium. Recent observations at very high (TeV) gamma-ray energies have shown that pulsar nebulae constitute the dominant high energy population in our Galaxy. The implications of these observations for the nature of pulsar nebulae will be discussed.