In France, bakeries usually have signs in the windows that prominently say “Boulangerie” and “Patisserie.” A boulangerie is a bakery that specializes in breads. A patisserie is a bakery that specializes in pastries. The majority do both and offer a wide selection of both sweets and baguettes and other breads. Some bakeries also display a sign that says “vienoisserie,” usually without much explanation. Vienoisserie means Vienna-style baked goods, but includes many things that are very typically French. They are pastries made with doughs that are “dry” and rich in butter, and would include a pastry made with brioche dough, as opposed to a cake-type pastry that begins with a very wet batter. Vienoisserie also includes pastries that are made with with yeasted, laminated dough that alternates layers of flour/pastry dough and butter. These pastries include things like croissants, Danishes, pain au chocolate (both often made with croissant dough).
Vienoisseries are usually eaten as breakfast or as a snack and not as a dessert because they are not too sweet. Even treats like pain au chocolate and brioche au sucre are not sweetened, despite their respective additions of chocolate and sugar. The main flavor of pastries like this is butter, and they are generally known for the lightness of the pastry, whether you are dealing with a flaky croissant or a soft brioche bun.
It is worth noting, as commenter Susan Betz mentioned to me, that a similar term is also used in the US and Canada. She said, “As an interesting contrast, in both the US and Canada, the term Viennese Buffet is sometimes used for a selection of desserts. It is frequently, though not exclusively, of individual servings as opposed to slices of a larger baked item. I have been to a wedding in Toronto that ended with this and have seen it offered at major hotels here in the states. It is akin to what a more casual restaurant would call a dessert bar.”