Let's face it: if you're here, you're likely at least a little bit of an art history or design nerd. In which case, you may be familiar with the terms art deco and art nouveau, or at least with their representation in popular culture.
For example, the roaring 20's, flapper aesthetic that comes in and out of contemporary fashion, as with the recent Leo make-over of the Great Gatsby, is Art Deco. This style transcends media categories, meaning it can be seen in architecture, fashion, the visual arts, design and more.
Art Nouveau is kind of like art deco's slightly weird, slightly witchy, nature-loving hippie aunt. It pre-dates Art Deco as it was the popular style from around 1900-1920. In fact, the German version is called Jugenstil, meaning the art of the youth. This aesthetic is most commonly recognized in the work of artists like Alphonse Mucha, the Vienna Secessionists, the architecture of Gaudi in Spain, and the strange iron-work of the Paris Metro. Why do I say weird, and slightly witchy? Art Nouveau is inspired by nature, but also in a kind of blurring of boundaries between nature and the man-made world. That is why you see so many representations of women as butterflies, or with fairy wings, and why the forms of the Paris metro stops look almost like giant insects. This is the strange part, as there are definite themes of mutation from human to insect, or animal. The centaur in particular was a popular mythical figure during this time in popular culture and in art.
In design terms, the difference between these two easily confused early 20th century movements is about line and form. Art Nouveau uses organic, or curving lines and asymmetry that is found in nature. Art Deco uses sharp, straight lines and symmetrical geometry. Think the architecture of Miami Beach.