  An overview is presented of the main properties of dark matter haloes, as we
know them from observations, essentially from rotation curves around spiral and
dwarf galaxies. Detailed rotation curves are now known for more than a thousand
galaxies, revealing that they are not so flat in the outer parts, but rising
for late-types, and falling for early-types. A well established result now is
that most bright galaxies are not dominated by dark matter inside their optical
disks. Only for dwarfs and LSB (Low Surface Brightness galaxies) dark matter
plays a dominant role in the visible regions. The 3D-shape of haloes are
investigated through several methods, that will be discussed: polar rings,
flaring of HI planes, X-ray isophotes.
  It is not yet possible with rotation curves to know how far haloes extend,
but tentatives have been made. It will be shown that the dark matter appears to
be coupled to the gas in spirals and dwarfs, suggesting that dark baryons could
play the major role in rotation curves. Theories proposing to replace the
non-baryonic dark matter by a different dynamical or gravity law, such as MOND,
have to take into account the dark baryons, especially since their spatial
distribution is likely to be quite different from the visible matter.
