Voice Control With Hey Siri
You can use Siri with the AirPods, and if you own AirPods 2, you can simply say "Hey Siri" instead of double-tapping on one of your AirPods.
You'll need to train Hey Siri on your iPhone, and then all you need to do is say, "Hey Siri" with at least one AirPod in and you have full access to Siri on your ear.
This is way easier than using your Apple Watch or picking your iPhone up out of your pocket. It's perfect for getting directions, sending a message or starting a call while you are walking or working in the yard.
If you need to turn on "Hey Siri" on your iPhone, go to Settings -> Siri & Search -> Listen for Siri -> On. Siri will only respond to your voice, so you don't need to worry about someone else triggering Siri by talking near your ear.