Viennoiserie means literally something made "à la Viennoise", Vienna-style, since croissants (the typical viennoiserie) originated in Austria and not in France. By extension, in France "viennoiseries" are the type of "dry"pastries made from puff pastry or brioche dough, and they are typically eaten in the morning for breakfast, or sometimes as an afternoon snack, but never for dessert at the end of a meal. Dessert pastries in France tend to be more sophisticated, i.e. filled with mousse, buttercream, ganache, etc. Basically viennoiseries are baked items that are simple to eat on the go, don't necessitate the use of flatware/plates to be eaten, and can be eaten warm or cold.