When you hear a ringing tone indicating an incoming call, simply double tap the outside of either AirPod to answer it. When you're finished, the action is the same -– just double tap an AirPod to hang up the call. That's all there is to it, though you may also want to enable a setting to have your AirPods announce who is calling. Instructions are available here.
Apple's Beats brand in April unveiled the Powerbeats Pro, a redesigned wire-free version of its popular fitness-oriented Powerbeats earbuds.