This style was popular between the years 1890 - 1910. The style included organic shapes and elements inspired by nature. The use of curving metal shapes and glass was inspired by the new possibilities of the industrial revolution.
This style is similar in some ways to Art Deco, but not the same. Art deco is known for geometric shapes, but Nouveau is known for organic shapes.
One of the most iconic Art Nouveau architects was Antoni Gaudí. You have probably seen pictures of Barcelona's Casa Batlló which was transformed under a renovation by him.
To learn more about this project of his see the link below:
Another well-known architect and designer, Victor Horta, created beautiful exteriors, interiors, and furnishings in this style. You have likely seen his interior designs if you have ever searched for Art Nouveau on the internet. Many of his interior works were of townhouses for the elite Belgians. His use of organic shapes and glass for natural lighting creates an inviting environment. The furnishings have rounded edges and natural elements.
"Art Nouveau was influenced by experiments with expressive line by the painters Paul Gauguin and Henri de Toulouse-Lautrec. The movement was also partly inspired by a vogue for the linear patterns of Japanese prints (ukiyo-e)."
The term Art Nouveau was created in Belgium and. This style was intentionally created to be a new type of art unlike the popular historic styles of the period. I suppose you could say it was a sort of rebellion. The ornate and ornamental features of this period have become inspiring and unforgettable.