What is a chatbot for website? How do they work:A complete guide for beginners

"There is an endless number of a chatbot for website creation platforms online. According to Facebook's count, more than 33,000 bots operating across the industry, and it is predicted that over 85% of customer engagement is going to be without human intervention." Most of the people have heard of chatbot for technology but are unable to understand what exactly they are. What is the need to use chatbots on websites, or why are they important? How to build a chatbot?