Origins and Interpretation of Tidal Debris
  The stellar debris structures that have been discovered around the Milky Way
and other galaxies are thought to be formed from the disruption of satellite
stellar systems --- dwarf galaxies or globular clusters --- by galactic tidal
fields. The total stellar mass in these structures is typically tiny compared
to the galaxy around which they are found, and it is hence easy to dismiss them
as inconsequential. However, they are remarkably useful as probes of a galaxy's
history (as described in this chapter) and mass distribution (covered in a
companion chapter in this volume). This power is actually a consequence of
their apparent insignificance: their low contribution to the overall mass makes
the physics that describes them both elegant and simple and this means that
their observed properties are relatively easy to understand and interpret.
