Behind one of the world's most popular cryptocurrencies (Bitcoin) is blockchain technology, which is revolutionizing the world and bringing significant changes in the technological and business environment. Blockchain is an immutable and decentralized peer-to-peer system that can track and verify digital transactions. The idea is to bring transparency, security and data integrity to it. It finds its application in almost all domains, from finance, education, energy, supply chain, healthcare and many others. This paper elaborates on the various components that make this technology reliable and credible and provides an insight into the various application areas of blockchain technology. In addition to a detailed description of blockchain technology, it also outlines the shortcomings, challenges and threats faced by this technology. One of the emphasis of this paper is to provide a comprehensive study of the chronological evolution of Blockchain technology highlighting the details of each generation. In addition, it shows the differences between these generations according to parameters ranging from the utility of basic principles, consensus mechanisms and smart contracts to energy and cost requirements and speed of execution and scalability.