Upon selecting the centerline, section dimensions display at each endpoint. They provide the area and position relative to the centerline for each selected section.
To see whether the centerline is normal to the section, use Area Loft. The section dimension points to a section that is normal to the centerline.
In addition to these two sections, you can add placed sections to define cross-sections that control the shape of the loft.
Typically, you use Placed Sections as Driving Sections.