Yoga Nidra is a form of meditation that uses awareness and relaxation to calm and soothe the body and mind. It's also known as yogic sleep, which is why it falls under the category of pratyahara. Yoga Nidra takes you through a guided meditation where you're asked to focus on your breathing, relax your muscles, and allow any thoughts or worries to drift away.
Use this Yoga Nidra Sleep meditation before falling asleep, you can also do it as a sort of "energy nap" where you practice only for the length offered, or stay in it for another 20 minutes with the meditation music that follows, and come out feeling refreshed and revitalized. This lets your body feel like it's fallen asleep while your mind floats between sleep and awakeness, connected to a sense of love and wellbeing.