Chatbots, also called chatterbots are applications that simulate human conversation either taking voice or text commands or both as input. They are automated programs that utilize Natural language processing techniques to understand process and responds accordingly to the users. Chatbots are cost effective and require a very little investment cost in the beginning stage of development. The software program can be built using AIML that use Extensible Mark-up Language as a base. In python, libraries like NLTK and JSON package can be used for the efficient designing of a Chatbot model. Chatbots use Corpus which is the vocabulary or the huge amount of data from different human dataset to the model. This paper elaborates on a Chatbot model that uses the functions of nltk library in python to pre-process data and responds accurately to the user using the cosine similarity approach. This chatbot can be implemented for any specific domain by changing the corpus. The corpus used in this design is about chatbots itself. The chatbot is capable of accurately responding to the queries related to chatbots. Accuracy of the proposed chatbot is 93% that is out of 150 queries it answered 140 queries correctly.