  We consider general physical characteristics of doubly heavy baryons: the
spectroscopy in the framework of potential approach and sum rules of QCD,
mechanisms of production in various interactions on the basis of fragmentation
model with account of preasymptotic corrections caused by higher twists over
the transverse momentum of baryon, inclusive decays and lifetimes in the
operator product expansion over the inverse powers of heavy quark masses as
well as the exclusive decays in the sum rules of QCD. We generalize the methods
developed in the effective theory of heavy quarks towards the description of
systems with two heavy quarks and a single light quark. The calculations are
presented for the masses, decay widths and yields of baryons with two heavy
quarks in the running and planned experimental facilities. We discuss the
prospects of search for the baryons and possibilities of experimental
observation. The most bright physical effects concerning these baryons as well
as their position in the system for the theoretical description of heavy quark
dynamics are considered.
