It's high time we set the record straight: the word "macaron" is not an alternate spelling of macaroon. In fact, the two terms refer to distinctly different things. Both macarons and macaroons are confections, and both names are derived from ammaccare, which is Italian for "to crush" — but that's where the similarities end.
A macaron specifically refers to a meringue-based cookie made with almond flour, egg whites, and granulated and powdered sugar, then filled with buttercream, ganache or fruit curd. The delicate treat has a crunchy exterior and a weightless interior with a soft ending that's almost nougatlike in its chewiness. To add to the confusion, it's often called a French macaroon.
In contrast, the word macaroon is a generic phrase that is applied to a number of small, sweet confections. Mostly, the term is equated with the moist and dense coconut macaroon, which is composed of egg whites, sugar, and dried coconut, often piped with a star-shaped tip, and sometimes dipped in chocolate. The coconut macaroon, or congolais, as it's known in France, is frequently served during Passover because it contains no flour.
Source: Sara Yoo and Anna Monette Roberts