Custard is a creamy dessert made from a mixture of milk or cream, eggs, sugar, and vanilla. It is typically cooked on the stovetop or baked in the oven until it thickens to a smooth consistency. On the other hand, mousse is a light and airy dessert made by folding whipped cream or egg whites into a base mixture of ingredients such as chocolate, fruit puree, or gelatin. Mousse has a fluffy texture and is often chilled before serving. While custard has a rich and velvety mouthfeel, mousse offers a lighter and more delicate experience.