Agent
An agent is a system that uses a model to choose actions toward a goal, then responds to what happens. How much freedom it has depends on the application.
[Anthropic]In practice
A support assistant looks up an order, checks its delivery status, then decides whether more information is needed.
[Anthropic]A little deeper
Here we use agent for a system with model-directed steps. Some authors also include more prescribed workflows under the same name. [Anthropic]
Helpful to know: Language Model