Importation is what happens when goods are purchased from a foreign country to be sold at home. The importation of cars into the U.S. is what makes it possible for you to buy a Honda or a BMW.
If two countries have a trade agreement, it means they've worked out a deal for importation and exportation. When lobster is shipped from Maine and sold in China, that's exportation, and when macarons are baked in Paris and sold in New York, that's U.S. importation. The noun importation comes from the verb import, which first meant "convey information" and then "bring in goods from abroad," from the Latin portare, "to carry."