Standard trading conditions are like rules that must be followed when buying or selling something. They tell you how you must pay for the product, when and how you can return it, how much it costs, and who pays for shipping. Basically, all of the important details of the sale should be written down so that both the buyer and the seller know what to expect. By agreeing to trade with standard trading conditions, everybody knows what to expect and can trust that the other person will stick to those rules.