Artificial Conversational Entity are typically used in dialog systems for various practical purposes including customer service or information acquisition. Some chatterbots use sophisticated natural language processing systems, but many simpler systems scan for keywords within the input, then pull a reply with the most matching keywords, or the most similar wording pattern, from a database.
Artificial Conversational Entity are part of virtual assistants such as:
Which are accessed via many organizations' apps, websites, and on instant messaging platforms such as Facebook Messenger. Non-assistant applications include chatbots used for entertainment purposes, for research, and social bots which promote a particular product, candidate, or issue.