Chatbots have been used in instant messaging (IM) applications and online interactive games for many years but have recently segued into business-to-consumer (B2C) and business-to-business (B2B) sales and services. Chatbots can be added to a buddy list or provide a single game player with an entity to interact with while awaiting other "live" players. If the bot is sophisticated enough to pass the Turing test, the person may not even know they are interacting with a computer program.
You can structure these modules to flow in any way you like, ranging from free form to sequential. The Bot Framework SDK provides several libraries that allows you to construct any conversational flow your bot needs. For example, the prompts library allows you to ask users for input, the waterfall library allows you to define a sequence of question/answer pair, the dialog control library allows you to modularized your conversational flow logic, etc. All of these libraries are tied together through a dialogs object. Let's take a closer look at how modules are implemented as dialogs to design and manage conversation flows and see how that flow is similar to the traditional application flow.
A virtual assistant is an app that comprehends natural, ordinary language voice commands and carries out tasks for the users. Well-known virtual assistants include Amazon Alexa, Apple’s Siri, Google Now and Microsoft’s Cortana. Also, virtual assistants are generally cloud-based programs so they need internet-connected devices and/or applications in order to work. Virtual assistants can perform tasks like adding calendar appointments, controlling and checking the status of a smart home, sending text messages, and getting directions.

How: this is a relatively simple flow to manage, and it could be one part of a much larger bot if you prefer. All you'll need to do is set up the initial flow within Chatfuel to ask the user if they'd like to subscribe to receive content, and if so, how frequently they would like to be updated. Then you can store their answer as a variable that you use for automation.

For each kind of question, a unique pattern must be available in the database to provide a suitable response. With lots of combination on patterns, it creates a hierarchical structure. We use algorithms to reduce the classifiers and generate the more manageable structure. Computer scientists call it a “Reductionist” approach- in order to give a simplified solution, it reduces the problem.

“We believe that you don’t need to know how to program to build a bot, that’s what inspired us at Chatfuel a year ago when we started bot builder. We noticed bots becoming hyper-local, i.e. a bot for a soccer team to keep in touch with fans or a small art community bot. Bots are efficient and when you let anyone create them easily magic happens.” — Dmitrii Dumik, Founder of Chatfuel

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.
Like apps and websites, bots have a UI, but it is made up of dialogs, rather than screens. Dialogs help preserve your place within a conversation, prompt users when needed, and execute input validation. They are useful for managing multi-turn conversations and simple "forms-based" collections of information to accomplish activities such as booking a flight.
A chatbot (also known as a spy, conversational bot, chatterbot, interactive agent, conversational interface, Conversational AI, talkbot or artificial spy 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 chatbots use sophisticated natural language processing systems, but many simpler ones scan for keywords within the input, then pull a reply with the most matching keywords, or the most similar wording pattern, from a database.