AIML, Artificial Intelligence Markup Language developed by Richard Wallace, constitutes an open standard for creating your own chat bot. AIML file consists of row-type, database-style data combined with hierarchical XML data in each response. This video shows one of spreadsheet-style editors for AIML, Simple AIML Editor (SAE) developed by Adeena Mignogna. The SAE allows botmasters to manage large AIML sets and then zoom in on the templates to edit the responses.
The word robot is derived from the Czech noun robota meaning “labor”, and is an accomplishment of the cubist painter and writer Josef Capek, older brother of novelist and playwright Karel Capek. The word robot first appeared in 1920 in the Karel Capek’s play “RUR” (“Rossum’s Universal Robots”) and since then this play popularized the word invented by playwright’s brother.
Since 2016 when Facebook allows businesses to deliver automated customer support, e-commerce guidance, content and interactive experiences through chatbots, a large variety of chatbots for Facebook Messenger platform were developed. In 2016, Russia-based Tochka Bank launched the world's first Facebook bot for a range of financial services, in particularly including a possibility of making payments.  In July 2016, Barclays Africa also launched a Facebook chatbot, making it the first bank to do so in Africa. 
24/7 digital support. An instant and always accessible assistant is assumed by the more and more digital consumer of the new era. Unlike humans, chatbots once developed and installed don't have a limited workdays, holidays or weekends and are ready to attend queries at any hour of the day. It helps to the customer to avoid waiting of a company's agent to be available. Thus, the customer doesn't have to wait for the company executive to help them. This also lets companies keep an eye on the traffic during the non-working hours and reach out to them later.
Previous generations of chatbots were present on company websites, e.g. Ask Jenn from Alaska Airlines which debuted in 2008 or Expedia's virtual customer service agent which launched in 2011. The newer generation of chatbots includes IBM Watson-powered "Rocky", introduced in February 2017 by the New York City-based e-commerce company Rare Carat to provide information to prospective diamond buyers.
The word bot, in Internet sense, is a short form of robot and originates from XX century. The modern use of the word bot has curious affinities with earlier uses, e.g. “parasitical worm or maggot” (1520s), of unknown origin; and Australian-New Zealand slang “worthless, troublesome person” (World War I -era). The method of minting new slang by clipping the heads off respectable words does not seem to be old or widespread in English. Examples: za from pizza, zels from pretzels, rents from parents, are American English student or teen slang and seem to date back no further than late 1960s.
You can find chatbots on many messaging apps, including Facebook Messenger, WhatsApp, Kik, and Telegram. Even the more work-focused service Slack has its own built-in bot that helps you set reminders and jot down notes. Twitter has bots too which will reply to you, but usually not offer any assistance. I've rounded up some of the top chatbots on each platform in the list below.
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.”
This chatbot aims to make medical diagnoses faster, easier, and more transparent for both patients and physicians – think of it like an intelligent version of WebMD that you can talk to. MedWhat is powered by a sophisticated machine learning system that offers increasingly accurate responses to user questions based on behaviors that it “learns” by interacting with human beings.
^ "From Russia With Love" (PDF). Retrieved 2007-12-09. Psychologist and Scientific American: Mind contributing editor Robert Epstein reports how he was initially fooled by a chatterbot posing as an attractive girl in a personal ad he answered on a dating website. In the ad, the girl portrayed herself as being in Southern California and then soon revealed, in poor English, that she was actually in Russia. He became suspicious after a couple of months of email exchanges, sent her an email test of gibberish, and she still replied in general terms. The dating website is not named. Scientific American: Mind, October–November 2007, page 16–17, "From Russia With Love: How I got fooled (and somewhat humiliated) by a computer". Also available online.