Pralines are confections made from nuts, whole or crushed, and sugar syrup. Most today have an added chocolate flavoring to them (particularly Belgian and French). In Europe, most pralines are made with almonds. In the US they generally use pecans. Really, any kind of nut can be used.
In the 17th century, at Chateau of Vaux-le-Vicomte (France), Marshal du Plessis-Praslin (who lived from 1598 to 1675) inspired the first praline when he came up with a caramelized sugar poured over almonds. The idea caught on. In fact, any food that contains ground nuts and sugar syrup is considered a praline. The action of crushing the nuts and placing them in sugar is called pralin. So pralines exist in cakes and even ice cream.
There are basically three types of pralines: Belgian, created with a hard chocolate shell and a soft or liquid inner core, French, made with almonds and caramelized sugar, and the American, made more like a fudge with any type of nut and the sugar made into a creamy or milky coating.
When the French colonized Louisiana they brought their recipes with them. Since nuts and sugar cane were readily available in the area it was only natural that they began producing pralines. New Orleans chefs substituted the pecan since it was easier to find and they added cream to the mixture to make it richer.
How to celebrate: Go buy some pralines, they are readily available at nearly any grocery or candy shop. Enjoy some praline ice cream. Make your own pralines from the recipe above.