What do the Passiflora extract and glycerin actually do for my skin during a shower?

Glycerin is a humectant: it attracts and holds water molecules. In a rinse-off product, it works during the minute or two the product sits on wet skin — it draws water into the upper layers of the stratum corneum, so when you rinse, the surface hasn't been stripped of all bound moisture. This is why you feel less "just washed and already dry." Passiflora incarnata (passion flower) extract brings flavonoids and phenolic compounds that, in leave-on cosmetics, are associated with soothing and antioxidant effects. In a wash-off format, its main role is sensory and conditioning: it deposits a very light, non-greasy film that improves skin glide after toweling and contributes to a smoother, more supple finish. Neither ingredient replaces a dedicated body moisturizer — their contact time is too short for deep barrier repair — but they shift the starting point so your lotion or oil works on skin that isn't already parched. If you have very dry or mature skin, you'll still want to apply a body cream within three minutes of stepping out of the shower while the skin is damp.