When people outside of architecture talk about new buildings they often call them "modern." But inside of architecture, that word uses a big "M" and refers to a specific era in which buildings and cities were built.
To architects, MODERNISM describes the period from the early 20th century to around 1970 when human culture grew rapidly with industrial manufacturing. These decades of tremendous global change shifted architecture in two basic directions: it allowed buildings to be made in new ways (out of materials like concrete, steel, and large expanses of glass), and it emphasized the development of cities and new kinds of infrastructure (to support air travel, power generation, skyscrapers, and cars).
Modern buildings can be identified not only by when they were built, but also by the use of clear shapes and unadorned surfaces. They often look more like obvious objects in a open area than disguised into the fabric of a city.
So what do architects call buildings built now? The general term is contemporary architecture. Notice the little "c"? The word "contemporary" doesn't refer to an era or a style, just to current projects. Era and style are seen only when we look back on architecture a few decades from now. Through the perspective of hindsight we're able to see more clearly what was really happening and what it means.