An AI agent is an LLM-powered system that plans, uses tools, and takes actions over multiple steps to complete tasks autonomously. Tools include APIs, code execution, web browsing, and file operations. Agents go beyond single-prompt question-and-answer to handle complex workflows requiring reasoning, tool use, and iterative correction. "Agentic AI" is the dominant 2025 frontier for AI applications and the next major capability layer beyond chat. Agents are what happens when LLMs stop just answering questions and start doing things.
What distinguishes agents from simpler LLM applications:
Multi-step reasoning: agents break complex tasks into steps and execute each.
Tool use: agents call APIs, run code, browse the web, query database...