Yaourt / yogurt
A few years ago, yaourt meant « yaourt nature » (plain yogurt), but nowadays, there are so many types of yaourt, it's difficult to know them all.
What you must keep in mind is that yogurt is made out of cow's milk but a lot of products in the yaourt section are so sweet, with so many added ingredients that you can't be sure that it's yaourt anymore. These products are more like a dessert than a yaourt, and it's often written "crème dessert" or "dessert lacté" on them.
Yaourts natures : just plain yaourt, nothing else unless it's written « sucré » (sugar added) on the
package.

You can also find « yaourt brassé », which is a yaourt nature but with a really thick creamy texture as if some cream had been added, but actually it's only cow's milk.
What's the difference between yaourt nature and yaourt brassé ? The shape of the package (!) and the texture, otherwise they're both plain yogurt but "yaourt brassé' is more creamy :

On the left : yaourt brassé, on the right : yaourt nature

You can also find « yaourt brassé », which is a yaourt nature but with a really thick creamy texture as if some cream had been added, but actually it's only cow's milk.
What's the difference between yaourt nature and yaourt brassé ? The shape of the package (!) and the texture, otherwise they're both plain yogurt but "yaourt brassé' is more creamy :

On the left : yaourt brassé, on the right : yaourt nature
How to use them : at the end of your lunch or dinner, (instead of the cheese), you can put some sugar in it.
Sometimes you can use it in dessert recipes (gâteau au yaourt).
Where to find them in a supermarket : "rayon frais", facing the "crème fraîche", or if not, next to the crème fraîche and beurre (butter).