Apple says its new H1 chip in the new AirPods is developed specifically for headphones, and "delivers performance efficiencies, faster connect times, more talk time and the convenience of hands-free "Hey Siri.”
By "50% more talktime," Apple means an extra hour of battery life during phone calls.
And as for "hands-free" Siri, it means you can summon Siri using just your voice. It's a significant change over what you had to do with the original AirPods to summon Siri, where you had to physically tap one of the pods.