VAPID, which stands for Voluntary Application Server Identity, is a new way to send and receive website push notifications. Your VAPID keys allow you to send web push campaigns without having to send them through a service like Firebase Cloud Messaging (or FCM). Instead, the application server can voluntarily identify itself to your web push provider.
Why make the switch to VAPID? You should find that it helps improve the overall performance of your web push notifications, specifically improving delivery rates, something that all web push users should be excited about. By streamlining the delivery process, you are lessening the chance of delivery errors along the way. VAPID will also help with security by encrypting your messages.
VAPID isn't just the future of web push delivery: its impacts are already being felt now. Some browsers, like Microsoft Edge, already require that you use VAPID keys instead of FCM keys. Switching to VAPID will immediately open you up to more opportunities for subscribers who come to you from Microsoft Edge.