CAD (Computer-Aided Design) in the BIM field refers to the use of software to create detailed 2D or 3D drawings and models of building systems and components. While CAD is primarily used for design and drafting, it serves as a foundational tool in the BIM process by providing the initial design layouts, which can later be integrated into a broader, more collaborative BIM model. CAD helps improve accuracy and efficiency in creating and modifying technical drawings.