A big puff vape is a pod kit designed to give thousands of puffs from a single device. They usually come with multiple 2ml pods or have a refillable chamber system that lets you vape for longer without swapping out the device or pod. Some offer up to 10,000 or even 20,000 puffs in total, that's way more than your average 600-puff disposable.
Most use built-in mesh coils for better flavour, rechargeable batteries, and either prefilled or refillable pods. They're the next step for vapers who want disposable-style convenience but with better value and less hassle.