ESO Astronomical Glossary - W
A white dwarf is a small, very dense, cold, dead star consisting mostly of carbon and oxygen. These faint stars are the remnants of red giant stars that lost their outer layers, forming a planetary nebula. White dwarfs are about the size of the Earth, but they are substantially heavier, with a mass typically equivalent to that of the Sun. The Sun will someday turn into a white dwarf.
Wolf-Rayet (W-R) stars are unusual stars that are very massive (over 40 times the mass of our Sun), extremely hot and very bright. These stars continually eject their outer atmosphere in bubble-like shells of particles and gas (creating a strong stellar wind). About 200 of these stars are known in the Milky Way. Wolf-Rayet stars were discovered in 1867 by C. J. Wolf and G. Rayet.