French ice cream is traditionally made with egg yolks, cream, and sugar before being churned.
French-style ice cream uses a custard base. The egg yolks are combined with dairy and sugar and gently heated, producing a richer mixture before it is cooled and frozen. The yolks also act as emulsifiers, helping create a smooth texture.
Philadelphia-style ice cream is the main contrast: it generally contains cream, milk, sugar, and flavoring without egg yolks. Gelato is an Italian frozen dessert made with its own customary balance of milk, cream, sugar, and flavorings, so it is not simply another name for French ice cream.
Recipes vary, and modern commercial products may not follow one strict national formula. The defining distinction in this comparison is the custard base containing egg yolks.