An AI agent does a job; a chatbot holds a conversation. A chatbot answers questions in a window and waits for the next one, so the work behind each question is still yours. An agent reads what comes in, decides the next step, acts in your tools and hands a person whatever falls outside its rules, so the only work left for your team is the exceptions.
Take the reports that land in a company's inbox every week. A chatbot could summarise one if somebody pasted it in. An email agent reviews each one as it arrives, produces the reports management reads, prepares the invoices, and stops for a person when something looks unusual.
That difference is also the honest test of whether you need an agent. If the job is answering the same few questions, a clear page on your website may be enough. If it is reading, checking, writing and sending every day, an agent is the right shape; when a chatbot helps, it is a small part of a larger agent.