  We present a short overview on the extragalactic background radiation from
radio to X-rays, with an eye to the relation to galaxy formation and
emphasizing on astrophysical backgrounds (as opposed to cosmological). As the
radio background, the wealth of data on source counts make possible reliable
estimations of the contribution from extragalactic sources. At 178 MHz we
obtain an antenna temperature of about 22 K, with the 60% of the flux
contributed by radiogalaxies and quasars and the remaining part from sub-mJy
radio sources. At high frequencies the compact sources, generally QSOs,
dominate. An intense far-IR/sub-mm background is predicted if a large fraction
of the hard X-ray Background (XRB) comes from starburst galaxies but this might
face problems with the upper limits on the far-IR isotropic flux. To clarify
the problem spectral measurements should be complemented with the analysis of
small scale anisotropies. The flattening of the QSO counts at B=19.5 suggests
that their contribution to the optical/near-IR background is small in
comparison to that of galaxies. As for the XRB, a consisting picture obtains
considering two AGN populations: a "soft X-ray spectrum" population and a "hard
X-ray spectrum" one, mainly contributing to the soft and to the hard XRB
respectively. A third population of extremely absorbed or of reflection
dominated AGN could either be the dominant contributor of the XRB above 3 keV.
