Chatbots are computer programs that you can have a conversation with, simply by chatting (or typing) as you would to another human being.
They are used in education, robotics, in call-centres, as online-assistants - the next time you visit a website and a box pops up asking if you need any help, ask yourself if this is a human or a chatbot you are talking to!
There are many chatbots online, that can converse on a multitude of subjects, and in many different languages, however they don't usually remember anything you tell them. For my MSc research project I created a chatbot with long-term memory - Bob, a Space & Solar System loving robot who longs to be human. Since this was a few years ago, he is now getting old and in need of an upgrade. However, you can still chat to a more forgetful version of Bob here.