Wolf Rayet Stars (discovered by C. Wolf and G. Royet in 1867) are very hot stars (T > 70,000 K). The spectra of WR stars have no absorption (dark) lines. It shows a broad emission lines of Hydrogen and ionized Helium, Carbon, nitrogen and oxygen. It is believed that these stars have most their outer layers due to strong stellar wind. These are massive stars. Thus WR stars has exposed the stellar interior, which glues rise to a different spectrum than the normal outer layers. Many Wolf Rayet stars are found to be the member of binary systems.