Mousse is a dessert that's made of cream and eggs that have been whipped until they're light and creamy. Don't confuse the dessert mousse with the foamy hair product also called mousse, or else people will want to nibble on your hair after dinner.
If you have heavy cream, some eggs, and flavoring — plus a whisk or an electric mixer — you can make mousse. Most mousses are sweet, flavored with chocolate or fruit or peanut butter, but it's also possible to cook a savory mousse, like a salmon mousse or a chicken liver mousse. Because its texture is similar to these foods, the foamy hair product is also called mousse. In Old French, mousse means "froth," but also, unappetizingly, "scum."