These terms describe art works and architectural structures of a certain era, both are aesthetically pleasing in their own rights. Prior to moving to the UK I had never heard of these terms; I know, how ignorant of me? Well better late than never.
Art Nouveau refers to the style movement which swept through western Europe and USA between 1880 and 1910. It was marked by sweeping curves, arches, the female form, floral patterns, heights and linear designs inspired by natural forms. The color scheme was muted and sombre.
Art deco on the other hand began in Europe in 1908 and lasted as a trend till the start of the second world war II (1930). Common features of art deco include angular and geometric shapes, black,chrome and bright colors, stylized images of cars and airplanes.
In my opinion, architecture from my parents generation were more art nouveau in style. I think we skipped the art deco period and went straight into modern styles.