  Many analyses at the collider utilize the hadronic jets that are the
footprints of QCD partons. These are used both to study the QCD processes
themselves and increasingly as tools to study other physics, for example top
mass reconstruction. However, jets are not fundamental degrees of freedom in
the theory, so we need an {\em operational jet definition} and {\em reliable
methods to calculate their properties}. This talk covers both of these
important areas of jet physics.
