Art nouveau is a special way for artists to make things look pretty. Like how you might draw a flower or a bird and color it in with lines that flow and swirl to make it look more interesting.
But with art nouveau, artists did this on a lot of different things, like buildings, furniture, and even everyday objects like lamps and dishes. They used special shapes that looked like vines and flowers, and they often used bright, bold colors.
This style became really popular a long time ago, in the 1890s. People liked it because it looked different from the stiff, old-fashioned things that were popular before. It was like a breath of fresh air!
Art nouveau didn't stick around forever, but it did influence a lot of other artists and designers who came after. And today, you can still see art nouveau in many beautiful buildings and designs all around the world.