A chatbot (also known as a talkbots, chatterbot, Bot, IM bot, interactive agent, or Artificial Conversational Entity) is a computer program or an artificial intelligence which conducts a conversation via auditory or textual methods.[1] Such programs are often designed to convincingly simulate how a human would behave as a conversational partner, thereby passing the Turing test. Chatbots are typically used in dialog systems for various practical purposes including customer service or information acquisition. Some chatterbots use sophisticated natural language processing systems, but many simpler systems scan for keywords within the input, then pull a reply with the most matching keywords, or the most similar wording pattern, from a database.
Screenless conversations are expected to dominate even more as internet connectivity and social media is poised to expand. From the era of Eliza to Alice to today’s conversational bots, we have come a long way. Conversational bots are changing the way businesses and programs interact with us. They have simplified many aspects of device use and the daily grind, and made interactions between customers and businesses more efficient.
ALICE – which stands for Artificial Linguistic Internet Computer Entity, an acronym that could have been lifted straight out of an episode of The X-Files – was developed and launched by creator Dr. Richard Wallace way back in the dark days of the early Internet in 1995. (As you can see in the image above, the website’s aesthetic remains virtually unchanged since that time, a powerful reminder of how far web design has come.) 
Authentication. Users start by authenticating themselves using whatever mechanism is provided by their channel of communication with the bot. The bot framework supports many communication channels, including Cortana, Microsoft Teams, Facebook Messenger, Kik, and Slack. For a list of channels, see Connect a bot to channels. When you create a bot with Azure Bot Service, the Web Chat channel is automatically configured. This channel allows users to interact with your bot directly in a web page. You can also connect the bot to a custom app by using the Direct Line channel. The user's identity is used to provide role-based access control, as well as to serve personalized content.
Keep it conversational: Chatbots help make it easy for users to find the information they need. Users can ask questions in a conversational way, and the chatbots can help them refine their searches through their responses and follow-up questions. Having had substantial experience with personal assistants on their smartphones and elsewhere, users today expect this level of informal interaction. When chatbot users are happy, the organizations employing the chatbots benefit.
There was a time when even some of the most prominent minds believed that a machine could not be as intelligent as humans but in 1991, the start of the Loebner Prize competitions began to prove otherwise. The competition awards the best performing chatbot that convinces the judges that it is some form of intelligence. But despite the tremendous development of chatbots and their ability to execute intelligent behavior not displayed by humans, chatbots still do not have the accuracy to understand the context of questions in every situation each time.

Chatbots can have varying levels of complexity and can be stateless or stateful. A stateless chatbot approaches each conversation as if it was interacting with a new user. In contrast, a stateful chatbot is able to review past interactions and frame new responses in context. Adding a chatbot to a company's service or sales department requires low or no coding; today, a number of chatbot service providers that allow developers to build conversational user interfaces for third-party business applications.
Amazon’s Echo device has been a surprise hit, reaching over 3M units sold in less than 18 months. Although part of this success can be attributed to the massive awareness-building power of the Amazon.com homepage, the device receives positive reviews from customers and experts alike, and has even prompted Google to develop its own version of the same device, Google Home.
The term "ChatterBot" was originally coined by Michael Mauldin (creator of the first Verbot, Julia) in 1994 to describe these conversational programs.[2] Today, most chatbots are 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.[3][4] 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.[5]