Agricultural extension is a service or system which assists farm people by the application of scientific research and knowledge to agricultural practices through farmer education. Extension is educational intervention so the role of extension service is invaluable in teaching farmers how to improve their productivity. Extension is also critical to move research from the lab to the field and to ensure a return on investment in research by translating new knowledge into innovative practices. The basic purpose of agricultural extension is changing the behaviour of farmers as desired and it makes them to adopt new technologies for increasing agricultural productivity. The knowledge of rural sociology is very essential for changing human behaviour. Rural sociology provides knowledge and understanding about the farmer and rural social system in which he lives. Rural sociology also helps in devising an agricultural extension plans for overall farmers development. The meaning of extension in India is transfer of technology. Communication has always been an integral part of agricultural extension. It is impossible to think of transferring technology or obtaining farmer feedback to adapt technology without communication. The purpose of Communication could be informative, persuasive and entertaining. Extension worker must have good communication skills for influencing people and convincing them to adopt the technology. The concept of adoption and diffusion helps to introducing new technologies and for speedy dissemination of technologies in rural areas. An extension worker’s job does not end with merely informing the farmers about improved practices, he should ensure with practical application of the results of research and field trials. For this purpose extension worker should understand the concepts of adoption and diffusion process and innovation by which the farmers accept new ideas in agricultural extension. The extension education helps all classes of people men, women and youth to solve their present and future economic, social and cultural problems. Without agricultural extension, farmers would lack access to the support and services required to improve their agriculture and other productive activities. For effective extension work extension worker need to have sound knowledge and understanding of concept of extension, rural sociology communication and adoption and diffusion of innovation.