AI agent

An AI agent is an autonomous software system that perceives its environment, makes decisions, and takes actions toward a goal. Unlike a plain script it has proactivity (initiates actions on its own), reactivity (responds to changes), and often social behavior (talks to other agents). Modern agents wrap an LLM for reasoning and planning, follow patterns like ReAct, and call external tools to touch the outside world. They may run alone or as part of a multi-agent system where each specializes.