People would type in their problems and how they were feeling. The application had very very simple logic that would follow up with a set series of statements or questions. Things like “that sounds tough” and “how does that make you feel?”.
People reported great satisfaction, even if they knew that the application had no smarts behind it. Because of course the whole time the magic of therapy lies in verbalizing your problems, with very little actively done by the therapist.
Now you can pay an LLM subscription for a service that likely produces worse results since it is tuned to be aggressively (and insidiously) sycophantic.