In today's world, companies are under increasing pressure to take care of the environment. As technology continues to advance, businesses are discovering new ways to reduce their carbon footprint and contribute to a more sustainable future. One of the solutions that have been gaining momentum in recent years is cloud computing. By moving data and applications to the cloud, companies can reduce their energy consumption, minimize waste, and contribute to a greener world. Cloud computing is a dynamic area of information and communication technologies (ICT) that brings new environmental challenges. Cloud computing technologies have a wide range of applications because they offer scalability, are reliable and trustworthy, and provide high performance at relatively low cost. The cloud computing revolution is reshaping modern networking and offers promising prospects for environmental protection as well as economic and technological benefits. These technologies have the potential to improve energy efficiency and reduce carbon footprint and (e-)waste. These characteristics can transform cloud computing into green cloud computing. In this review, we provide an overview of the key achievements of Green Cloud Computing. First, an overview of cloud computing is given. Then, recent studies and developments are summarized, and environmental issues are specifically addressed. Finally, future research directions and open problems related to green cloud computing are explained.