Difference between CAD and BIM?

3D CAD describes buildings by 3D views such as elevations, plans and sections.

With usual 3D CAD editing elevations, plans and sections requires you to check and update all the other views, which is error-prone and time-consuming.

CAD is based on 2D drawing elements and has evolved to 3D whereas BIM involves modelling in 3D with intellgent data parameters being assigned to individual members. To work in a BIM environment you need to work in 3D. This forms the fundamentals of working in a BIM environment. BIM integrates both the drafting and design process to make projects more efficent in achieving the project deliverables.

CAD 3D drawings are graphical entities only, whereas BIM carries much more information about the building (e.g. project life-cycle).