Cassata is a very rich, fancy sponge (pan di spagna) cake, filled or layered with ricotta flavoured with lemon, liqueur, chocolate, sliced almonds etc, depending on the recipe, then artistically frosted with marzipan and decorated with candied fruit in elaborate forms and colours.
Around Naples, cassata means a flavour of ice cream with candied fruits. The cake itself may have originated in the area: the first known depictions, from the 1st-century [AD], were found on a fresco and on a papyrus with a recipe in the Villa Oplonis, once a holiday home of Nero's wife, at Villa di Torre Annunziata near Pompeii.
Mini ones are cassatine.
In Cleveland, Ohio (where many southern Italian immigrants settled in the 19th and 20th centuries) you can also find a 'Cleveland cassata'—a light sponge filled with fresh strawberries and custard and topped with whipped cream.
Images by Michele Ursino, Wikipedia, Creative Commons License