The difference between a consultant who writes you a report and a colleague who does the work. Both are smart. Only one opens the spreadsheet, fixes the numbers and sends the email.
An agent is a model plus a harness plus tools. Given a goal, it gathers what it needs, takes an action, looks at the result, and decides the next step. It repeats this until the goal is reached or it needs you. That cycle is the agent loop. The word “agentic” simply means “works like this”.
A chat website is not an agent: you ask, it answers, the end. Claude Code is an agent: you ask, it works, you review.
Example
“Rename every photo in this folder to the date it was taken.” A chat gives you instructions. An agent lists the folder, reads the date from each file, proposes the new names, asks for your go-ahead and renames them. Two minutes instead of an afternoon.
Why it matters for you
Working with an agent is a different habit from chatting. You describe outcomes, not steps. You point it at the right folder. You review what it did rather than typing it yourself. Most of this course is about building that habit, because once you have it, the tool you use matters far less than you think.
Related
- Agent loop - gather context, act, check, repeat
- Harness - the program that runs the loop
- Tool - what an agent can actually do
- Claude Code - the agent used in this course