However, if you’re trying to develop a sophisticated bot that can understand more than a couple of basic commands, you’re heading down a potentially complicated path. More elaborately coded bots respond to various forms of user questions and responses. The bots have typically been “trained” on databases of thousands of words, queries, or sentences so that they can learn to detect lexical similarity. A good e-commerce bot “knows” that trousers are a kind of pants (if you are in the US), though this is beyond the comprehension of a simple, untrained bot.
Consider why someone would turn to a bot in the first place. According to an upcoming HubSpot research report, of the 71% of people willing to use messaging apps to get customer assistance, many do it because they want their problem solved, fast. And if you've ever used (or possibly profaned) Siri, you know there's a much lower tolerance for machines to make mistakes.
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. 
2a : a computer program that performs automatic repetitive tasks : agent sense 5 Several shopping "bots" will track down prices for on-line merchandise from a variety of vendors.— Sam Vincent Meddis especially : one designed to perform a malicious action These bot programs churn away all day and night, prodding at millions of random IP addresses looking for holes to crawl through. — Jennifer Tanaka
Simple chatbots work based on pre-written keywords that they understand. Each of these commands must be written by the developer separately using regular expressions or other forms of string analysis. If the user has asked a question without using a single keyword, the robot can not understand it and, as a rule, responds with messages like “sorry, I did not understand”.
Cheyer explains Viv like this. Imagine you need to pick up a bottle of wine that goes well with lasagna on the way to your brother's house. If you wanted to do that yourself, you'd need to determine which wine goes well with lasagna (search #1) then find a wine store that carries it (search #2) that is on the way to your brother's house (search #3). Once you have that figured out, you have to calculate what time you need to leave to stop at the wine store on the way (search #4) and still make it to his house on time.
[In] artificial intelligence ... machines are made to behave in wondrous ways, often sufficient to dazzle even the most experienced observer. But once a particular program is unmasked, once its inner workings are explained ... its magic crumbles away; it stands revealed as a mere collection of procedures ... The observer says to himself "I could have written that". With that thought he moves the program in question from the shelf marked "intelligent", to that reserved for curios ... The object of this paper is to cause just such a re-evaluation of the program about to be "explained". Few programs ever needed it more.