We first of all thank L. Woltjer who inspired this review paper. We thank N. Bergvall, S. Charlot, T. Karlsson, B. Lanzoni, F. Legrand, J. Masegosa, N. Prantzos, J. Salzer, D. Schaerer, E. Skillman, C. Taylor, R. Terlevich, T.X. Thuan, M. Tosi and J. Vilchez for useful discussions. In particular we thank R. Guzmán for comments on an early draft version of this paper, and James Lequeux for a careful reading of the manuscript. We are grateful to F. Legrand, R. Terlevich and T.X. Thuan, for providing us with figures used in this review. S. Charlot is thanked for making the most recent update of the Bruzual and Charlot spectral evolutionary synthesis models available to us. G. Östlin acknowledges support from The Swedish Foundation for International Cooperation in Research and Higher Education (STINT). In writing this review we made frequent use of the NASA astrophysics data system (ADS) and the NASA/IPAC extragalactic database (NED), which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. We acknowledge the use of NASA's SkyView facility (http://skyview.gsfc.nasa.gov) located at NASA Goddard Space Flight Center. HST-images of I Zw18 and SBS 0335-052 were obtained from the archive at the Space Telescope Science Institute, which is operated by the association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555.
Appendix: A list of some used abbreviations and acronyms:
| BCD: | blue compact dwarf galaxy |
| BCG: | blue compact galaxy |
| C: | carbon |
| CDM: | cold dark matter |
| dE: | dwarf elliptical galaxy |
| dI: | dwarf irregular galaxy |
| dSph: | dwarf spheroidal galaxy |
| DLA: | damped Lyman alpha |
| E: | elliptical galaxy |
| ELG: | emission line galaxy |
| FBS: | first Byurakan survey |
| FOS: | Faint Object Spectrograph (HST istrument) |
| Fe: | iron |
| GC: | globular cluster |
| H: | hydrogen |
| He: | helium |
| HST: | Hubble Space Telescope |
| IGM: | intergalactic medium |
| IMF: | stellar initial mass function |
| IR: | infrared |
| IRAS: | infrared astronomical satellite |
| ISM: | interstellar medium |
| ISO: | infared space observatory |
| L*: | the characteristic galaxy luminosity in the galaxy luminosity funtion |
| LF: | luminosity function (of galaxies) |
| LMC: | Large Magellanic Cloud |
| LSBG: | low surface brightness galaxy |
| N: | nitrogen |
| O: | oxygen |
| QSO: | quasar, quasi stellar object |
| S: | Sulphur |
| SBS: | second Byurakan survey |
| SF: | star formation |
| SFR: | star formation rate |
| SFH: | star formation history |
| SMC: | Small Magellanic Cloud |
| SSC: | super star cluster |
| UV: | ultraviolet |
| VLA: | Very Large Array |
| WR: | Wolf-Rayet |
| XBCG: | extreme blue compact galaxy |
| Y: | helium abundance |
| Z: | metallicity, heavy element abundance |
| z: | redshift |