I don't know about you, but I know for most of my friends and I, no one sat us down and took us through the different types of knickers (panties), and when to wear what. I know this is true for many others because I often see those underwear lines and the unforgivable white under white.
Educate our girls by gifting them a copy of The Knickers (Panty) Guide. They'll love you for it.