[en] The present knowledge about heavy quark systems is applied to the top system - both toponium and open top. Properties of these systems are predicted. What can be learned from toponium about quarkonium physics under realistic experimental conditions is also discussed. The spectrum of toponium states is discussed: the expected excitation spectrum, the implications for probing the heavy quark potential, and an estimate of the fine and hyperfine splittings. Production and decay properties are discussed, particularly emphasizing the growing importance of electroweak effects on the decays of toponium states. The properties of low-lying open top mesons are also dicussed. Some more exotic possibilities are considered, particularly: (1) the influence of light charged or neutral Higgs-like scalars on toponium decays, (2) possible direct production of J = 1 (t anti t) P-states via the axial vector coupling of the Z⁰ to (t anti t), and (3) toponium - Z⁰ interference effects which would result if the mass difference between some toponium resonance and the Z⁰ were less than the width of the Z⁰. The present situation of the nonrelativistic potential between heavy quarks is discussed. 53 refs., 29 figs.,