One of the most complex difficulties in developing a chatbot is the need to understand what was said by the end user. A chatbot that can extract the essence of what the end user is trying to say, will have the capacity to answer sufficiently. Since this is the basic and most important layer for the development of a sophisticated Chatbot, it is important to understand, at least on a basic level, the industry's current strategies for handling natural language. In the Academic world there is an entire field of knowledge, located somewhere between Linguistics and Computer Science, that revolves around the attempt to "understand" natural language when using computers. This field is called NLP - Natural Language Processing.
A broad view of the technologies available to Chatbot developers will enable you to evaluate the quality of the tools that various Chatbot platforms have to offer.