This is a lot less complicated than it appears. Given a set of sentences, each belonging to a class, and a new input sentence, we can count the occurrence of each word in each class, account for its commonality and assign each class a score. Factoring for commonality is important: matching the word “it” is considerably less meaningful than a match for the word “cheese”. The class with the highest score is the one most likely to belong to the input sentence. This is a slight oversimplification as words need to be reduced to their stems, but you get the basic idea.
By 2022, task-oriented dialog agents/chatbots will take your coffee order, help with tech support problems, and recommend restaurants on your travel. They will be effective, if boring. What do I see beyond 2022? I have no idea. Amara’s law says that we tend to overestimate technology in the short term while underestimating it in the long run. I hope I am right about the short term but wrong about AI in 2022 and beyond! Who would object against a Starbucks barista-bot that can chat about weather and crack a good joke?
The chatbot design is the process that defines the interaction between the user and the chatbot.[31] The chatbot designer will define the chatbot personality, the questions that will be asked to the users, and the overall interaction.[32] [33] It can be viewed as a subset of the conversational design.In order to speed up this process, designers can use dedicated chatbot design tools, that allow for immediate preview, team collaboration and video export.[34] An important part of the chatbot design is also centered around user testing. User testing can be performed following the same principles that guide the user testing of graphical interfaces.[35]

Chatbots can reply instantly to any questions. The waiting time is ‘virtually’ 0 (see what I did there?). Even if a real person eventually shows up to fix the issues, the customer gets engaged in the conversation, which can help you build trust. The problem could be better diagnosed, and the chatbot could perform some routine checks with the user. This saves up time for both the customer and the support agent. That’s a lot better than just recklessly waiting for a representative to arrive.
One of the first stepping stones to this future are AI-powered messaging solutions, or conversational bots. A conversational bot is a computer program that works automatically and is skilled in communicating through various digital media—including intelligent virtual agents, organizations' apps, organizations' websites, social platforms and messenger platforms. Users can interact with such bots, using voice or text, to access information, complete tasks or execute transactions. 
Interface designers have come to appreciate that humans' readiness to interpret computer output as genuinely conversational—even when it is actually based on rather simple pattern-matching—can be exploited for useful purposes. Most people prefer to engage with programs that are human-like, and this gives chatbot-style techniques a potentially useful role in interactive systems that need to elicit information from users, as long as that information is relatively straightforward and falls into predictable categories. Thus, for example, online help systems can usefully employ chatbot techniques to identify the area of help that users require, potentially providing a "friendlier" interface than a more formal search or menu system. This sort of usage holds the prospect of moving chatbot technology from Weizenbaum's "shelf ... reserved for curios" to that marked "genuinely useful computational methods".