This is where most applications of NLP struggle, and not just chatbots. Any system or application that relies upon a machine’s ability to parse human speech is likely to struggle with the complexities inherent in elements of speech such as metaphors and similes. Despite these considerable limitations, chatbots are becoming increasingly sophisticated, responsive, and more “natural.”
The term "ChatterBot" was originally coined by Michael Mauldin (creator of the first Verbot, Julia) in 1994 to describe these conversational programs. Today, most chatbots are either accessed via virtual assistants such as Google Assistant and Amazon Alexa, via messaging apps such as Facebook Messenger or WeChat, or via individual organizations' apps and websites.  Chatbots can be classified into usage categories such as conversational commerce (e-commerce via chat), analytics, communication, customer support, design, developer tools, education, entertainment, finance, food, games, health, HR, marketing, news, personal, productivity, shopping, social, sports, travel and utilities.
Three main reasons are often cited for this reluctance: the first is the human side—they think users will be reluctant to engage with a bot. The other two have more to do with bots’ expected performance: there is skepticism that bots will be able to appropriately incorporate history and context to create personalized experiences and believe they won’t be able to adequately understand human input.
Say you want to build a bot that tells the current temperature. The dialog for the bot only needs coding to recognize and report the requested location and temperature. To do this, the bot needs to pull data from the API of the local weather service, based on the user’s location, and to send that data back to the user—basically, a few lines of templatable code and you’re done.
Facebook Messenger chat bots are a way to communicate with the companies and services that you use directly through Messenger. The goal of chat bots is to minimize the time you would spend waiting on hold or sifting through automated phone menus. By using keywords and short phrases, you can get information and perform tasks all through the Messenger app. For example, you could use bots to purchase clothing, or check the weather by asking the bot questions. Bot selection is limited, but more are being added all the time. You can also interact with bots using the Facebook website.
The main challenge is in teaching a chatbot to understand the language of your customers. In every business, customers express themselves differently and each group of a target audience speaks its own way. The language is influenced by advertising campaigns on the market, the political situation in the country, releases of new services and products from Google, Apple and Pepsi among others. The way people speak depends on their city, mood, weather and moon phase. An important role in the communication of the business with customers may have the release of the film Star Wars, for example. That’s why training a chatbot to understand correctly everything the user types requires a lot of efforts.
Simply put, chatbots are computer programs designed to have conversations with human users. Chances are you’ve interacted with one. They answer questions, guide you through a purchase, provide technical support, and can even teach you a new language. You can find them on devices, websites, text messages, and messaging apps—in other words, they’re everywhere.
Closed domain chatbots focus on a specific knowledge domain, and these bots may fail to answer questions in other knowledge domains. For example, a restaurant booking conversational bot will be able to take your reservation, but may not respond to a question about the price of an air ticket. A user could hypothetically attempt to take the conversation elsewhere, however, closed domain chatbots are not required, nor often programmed to handle such cases.
The fact that you can now run ads directly to Messenger is an enormous opportunity for any business. This skips the convoluted and leaky process of trying to acquire someone's email address to nurture them outside of Facebook's platform. Instead, you can retain the connection with someone inside Facebook and improve the overall conversion rates to receiving an engagement.
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".