AI agent
Also called: agents
In one sentence
A system that pursues a goal by planning, choosing tools and taking actions — not just replying.
In more depth
The difference from a chatbot is action. An agent is given a goal, decides what to do, calls tools to do it, observes the results and continues until the goal is met or it stops.
That loop is what makes agents useful and what makes them risky: mistakes are no longer just wrong text, they are wrong actions in real systems.