Probably the most popular of them these days is called Alice - created by Richard Wallace. Alice uses AIML - a markup language designed specifically for designing chat Bot Messenger. Alice has been the competitor and winner in the Turning test many times. The Turing Test is a chat bot competition that pits Chat Bot Messenger against real humans. The trick is to fool the human to think he is talking to a real person. Although many creators win each year there is a consensus that there has not been one of them created yet that can actually fool a human being for very long. This is soon to change however with the never ending progress to create better artificial intelligence.
They are everywhere. Companies use them on their websites to promote their products. There are even virtual girlfriends these days for the lonely of heart who seek to create virtual relationships with cute avatars.
Why are they so important? They will eventually be needed to run in androids and robots. We all dream of the day when our android can speak to use about any topic we dream about. Creating smart androids and robots who can speak clearly is important and chat bots are the seed from which they will be created. So you see, they are very important to the future. Whoever can create the smartest and most fluid speaking bot will have created a stepping stone toward the future.