Green is the burning topic these days. In this paper, the authors present a brief overview of green computing. Green computing refers to supporting business critical computing needs with least possible amount of power or sustainable computing. This is a new paradigm of designing the computer system which considers not only the processing performance but also the energy efficiency. In the past, the sole focus was on IT equipments, processing power and associated equipment which includes infrastructure, power, cooling and data center space which was always assumed as readily available and affordable.