  We highlight and discuss the importance of accounting for nebular emission in
the SEDs of high redshift galaxies, as lines and continuum emission can
contribute significantly or subtly to broad-band photometry. Physical
parameters such as the galaxy age, mass, star-formation rate, dust attenuation
and others inferred from SED fits can be affected to different extent by the
treatment of nebular emission.
  We analyse a large sample of Lyman break galaxies from z~3-6, and show some
main results illustrating e.g. the importance of nebular emission for
determinations of the mass-SFR relation, attenuation and age. We suggest that a
fairly large scatter in such relations could be intrinsic. We find that the
majority of objects (~60-70%) is better fit with SEDs accounting for nebular
emission; the remaining galaxies are found to show relatively weak or no
emission lines. Our modeling, and supporting empirical evidence, suggests the
existence of two categories of galaxies, "starbursts" and "post-starbursts"
(lower SFR and older galaxies) among the LBG population, and relatively short
star-formation timescales.
