The physics of two-energy-component toroidal plasmas (TCT) is reviewed. Energy ''breakeven'' using the TCT mode (deuteron beams on a triton-target plasma) can be attained at much smaller ntau and temperature than in thermal plasma operation. This result reflects the fact that the fusion power density in a TCT can be much larger than in a thermal DT plasma of the same pressure. The large fusion power density (i.e., large neutron flux) of a TCT may find practical use in a number of applications. (auth)