Extremophiles include a diverse group with ability to survive in highly saline conditions, the halophiles. Halophiles are characterized in major life domains including Archaea as well as Bacteria. Archaea represents halophiles with heterotrophic, chemotrophic aerobes and anaerobes. A large number of members from these domains are found growing in diverse habitats including both thalassohaline and athalassohaline environment. Well-developed strategies of adaptation allow halophiles to sustain their survival in saline extremes. Certain important biotechnological and ecological features are grabbing the attention of scientists to study halophilic biology more deeply. This review presents overview of the halophilic biology with special focus on taxonomy, diversity, habitat, osmoadaptation and biotechnological applications of Bacteria and Archaea.