This book is designed for those researchers who want to do research in Natural Language processing but they are not sure about the research path. They have no idea about the concept of Machine Translation and their related types neither they have any knowledge of transformers and their various types. In this book we have summarize almost every type of transformers from oldest to latest which gives readers an exhaustive idea about the properties of the transformers. We have reviewed more than 100 research papers to bring the important detailed technical specification of transformers. We have conducted an exhaustive survey of different variants of transformers and have chosen approximately 60 very important transformers belonged to various classes which can be used for building machine translation models. In the next section we have also explained the challenges which are faced by low resource languages like Indian languages and why the research in these languages is slow. The low resource languages like different dialects of Indian languages are not implemented using NLP. Indian languages are morphologically rich languages and needed different ways to handle them. Some important challenges related to their translation are Ambiguity, Out of Domain Problem, lack of data is some of the major challenges which are discussed in this book. A lot of research opportunities are existing in exploring different dialects of Indian languages and one can do quality work in exploring himself in this direction. The tabular representation of every transformer will give reader an idea that to choose which one for him in his implementation.After going through this handbook I am very much sur.