These options allow you to choose different appearances of the linework of each drawing view:
EXACT is most commonly used, as exact geometry is projected from the 3D model and dimensions can be added accurately
CGR can be used if the exact geometry is not available, and only the tessellated CGR data exists
APPROXIMATE sacrifices the high quality for performance, especially with drawings of very detailed assemblies and/or many views.
RASTER provides for shaded views, instead of linework.