BIM - Building Information Modeling (3D intelligent building model)
2D - Something with 2 dimensions (i.e. flat)
3D - Something seen in 3 dimensions (i.e. width, length and height)
4D - Adding the aspect of Time to a project (Scheduling/Phasing)
5D - Adding the aspect of Cost to a project (cost estimating)
6D - Adding the aspect of Life Cycle Management (owner/FM)