A macaron is a French confection usually consisting of a creamy filling between two cookies. A macaroon is a light cookie often containing almonds or coconut. The two foods tend to share some of their ingredients—egg whites and almonds, especially—but the finished products differ greatly. Meanwhile, macaron tends to denote a very specific type of French cookie, while macaroon is more general, referring to a variety of cookies made around the world.
The French word and the English word share an origin in the Italian macarrone, but they have had separate meanings at least since the 19th entury.