is a dialog system that can communicate text- or speech-based.
It is usually used to respond to queries in an automated manner. No human labour is required for the handling of the requests. Depending on the setup, the chatbot acts independently. To handle different queries, the chatbot uses knowledge bases, or behavior patterns, to provide an appropriate response. Its level of knowledge is therefore dependent on the maintenance of these databases and the stored rules that the chatbot must follow.
Add AI (Artificial Intelligence) to these simple recognition patterns and it is actually possible for the chatbot to learn on its own.
The implementation of really good chatbots is therefore very complex.