These are images of a skirt I made in College, as you can see in the pictures there is a waist facing, an interfacing and a retainer row.
Retainer row: The stitching you can see just below the seam. Stops the facing from rolling up at the seam.
Waist facing: The fabric inside the garment that encloses the raw edge of the fabric.
Interfacing: Light, Medium or Heavy, it is sewn to the facing to stiffen an area of garment. It is often used to stiffen collars, cuffs, and waist facings, etc. The heavy weight interfacing is used to help hold the structure of a garment and keep it's bold shape.
I think I should have sewn the retainer row closer to the seam than I did, however I feel my poor sewing skills are gradually improving with practise. :)