What actually is an AI agent, in plain language?

An AI agent is an AI model that works toward a goal by deciding its own steps and using tools, where a chatbot answers one message and waits for the next. Anthropic draws the line this way: in a workflow, code fixes the steps; in an agent, the model directs its own process and tool use. In practice an agent opens a browser, reads your email or files, runs code or edits a spreadsheet, checks the result and carries on until the job is done or it needs you, as ChatGPT Work, Claude and Tasks in Gemini now do. For you it means handing over a whole task rather than a question, then checking what it did before trusting it with money or messages.