Juli Clover, writing for MacRumors:
Find My AirPods adds your AirPods to the “Find My iPhone” app, listing them alongside all other Apple products. In the app, you can tap on the AirPods to cause them to play a little chirping sound that gradually gets louder for location purposes.
After activating the sound, you can choose to have it play solely through the left AirPod or through the right AirPod so you don’t need to listen to chirping if only one of the AirPods is missing.
This is a really neat little feature for AirPods owners.