The basics
A chatbot is a computer program that holds a conversation with people through text or voice, ranging from simple scripted menus to AI assistants.
Chatbots have existed since the 1960s, when a program called ELIZA echoed people's sentences back as questions. For decades most chatbots followed scripts: pick an option, get a canned reply. They broke as soon as you typed something unexpected, which is why so many of them were frustrating.
Modern chatbots like ChatGPT, Claude, and Gemini (as of 2026) are built on large language models. They do not follow a script. They generate each reply word by word based on your message, the earlier conversation, and patterns learned from vast amounts of text. That is why they can handle almost any topic.
A chatbot is the interface; the model is the engine. The same model can sit behind a chat window, a voice assistant, or an app feature with no chat at all. Chatbots also forget everything when the conversation ends, unless a memory feature has been added.
The little chat window on a pizza company's site that takes your order and answers 'is the veggie one vegan?' is a chatbot.