Alright kiddo, so have you heard of negotiating before? It's when two or more people or groups talk to each other and try to come up with a deal or agreement that will work for everyone.
Well, a chief agricultural negotiator is someone who is in charge of negotiating deals specifically related to agriculture. Agriculture means farming and growing crops and animals for food.
So let's say there's a big meeting with people from different countries who all want to trade agricultural products with each other. The chief agricultural negotiator is the one who represents their country in those talks and tries to get the best deal possible for their farmers and food producers.
They might talk about things like import taxes (which are sort of like extra fees you have to pay to bring products from one country into another), or how much of certain food products can be traded between countries.
It's a pretty important job because agriculture is a big part of many countries' economies, and the negotiator has to make sure their country's farmers and food producers are getting a fair deal while also trying to make sure everyone else at the negotiating table is happy too.