Accelerators have become an important agent for the growth of new Startups across the world. They provide training and mentorship to startups and help them find investors. However the very nature of accelerators is evolving as they are trying to evolve sustainable Business Models. Through an in depth literature review, we try to explore a deeper understanding about the various types of Accelerators across the world and how they help startups. Also, through a worldwide survey to accelerators landscape, we identify their opinion about major challenges for the future, and through statistical exploration, provide an anatomy of these entrepreneurial firms. Therefore, this research provides a complete portrait on accelerators, regarding their business models, strategies and challenges for the future.