I find Yoga Nidra (or Yogic sleep) to be such a beautiful and restorative practice. It focuses on your physical body, as well as your subtle and energy bodies. These are all known as koshas, or sheaths, and nurtured within the practice. The practice is not focusing on asana or sleep in and of itself, but laying down and setting an intention, tuning into points of your body, your breath, energy, and mind, and allowing your full being a space to rest while you are settling into a calming and soothing awareness.
Not sure if this is the best explanation but I did my best and hope that it inspires a quest to learn more and that you may enjoy this practice!