The elevation field determines the source of z values used when drawing features in the profile and/or 3D viewer. The source of the z values can originate in the vertices of the geometry (i.e., 3D feature layer) or can be selected from an attribute or field. When using a field to define the z values for features, the same z value is used for the entire feature and it will appear parallel (i.e., flat) to the XY plane.