Different technical institutes and trade associations have over the years developed and codified their own set of specifications that now constitute the standard for their respective countries/geographical locations. We apply the relevant standards based on your work environment. Some examples are:
Until just about a decade ago, building designs were mostly 2D affairs, with entire structures, their plans and parts, being visualized and rendered in two-dimesional drawings. BIM on the the other hand is 3D. BIM softwares such as Tekla Structures allow us to simulate projects as they would appear in the real world, going beyond mere geometry and considering spatial relations. This, of course, is a very simplistic explanation, beacause BIM in fact is much more than just 3D.
BIM is an entire process that allows us to integrate consideration of time, money and environmental sustainability into our designs as well. With BIM we can model not only the structure itself but also its entire life-cycle from conceptualization to erection to renovation and demolition. Most crucially, however, BIM facilitates collaboration, which is invaluable in today's globalized world, where Architecture, Engineering and Construtions are all outsourced to companies miles apart.