  Orbital resonances are ubiquitous in the Solar system. They play a decisive
role in the long term dynamics, and in some cases the physical evolution, of
the planets and of their natural satellites, as well as the evolution of small
bodies (including dust) in the planetary system. The few-body gravitational
problem of hierarchical planetary-type systems allows for a complex range of
dynamical timescales, from the fast orbital periods to the very slow orbit
precession rates. The interaction of fast and slow degrees of freedom produces
a rich diversity of resonance phenomena. Weak dissipative effects --- such as
tides or radiation drag forces --- also produce unexpectedly rich dynamical
behaviors. This paper provides a mostly qualitative discussion of simple
dynamical models for the commonly encountered orbital resonance phenomena in
the Solar system.
