Chatbots are also referred to as virtual assistance devices. They are the basic forms of artificial intelligence software that can imitate human conversations. Chatbots are relatively a new technology. The main goal of this survey paper is to provide the information about the various existing chatbots and their history of evaluation, and the applications of various chatbots in different domains. Chatbots are applied in fields like medical, E-commerce, business, education, banking, customer services, entertainment, etc. Chatbots cab be analyzed and improved. Main goal of any chatbot is to allow the user to make a natural conversation with machine. A conversational system consists of dialogue management, speech recognition, speech synthesis and conversation generation.