  We review the theory of Higgs bosons, with emphasis on the Higgs scalars of
the Standard Model and its non-supersymmetric and supersymmetric extensions.
After surveying the expected knowledge of Higgs boson physics after the
Tevatron and LHC experimental programs, we examine in detail expectations for
precision Higgs measurements at a future e+e- linear collider (LC). A
comprehensive phenomenological profile can be assembled from LC Higgs studies
(both in e+e- and gamma-gamma collisions). The Giga-Z option can provide
important constraints and consistency checks for the theory of electroweak
symmetry breaking.
