The Lock screen exists in between states, when your iPhone or iPad is no longer asleep, but is also not yet open and fully functional. It can protect your device from unauthorized access and actions by a simple slide-to-unlock gesture, by a 4 number pin-code, by a strong alpha-numeric password, or Apple's Touch ID fingerprint identity scanner. Yet the Lock screen can be functional as well. If you want to, you can access Notification Center and Control Center, the Camera, and Siri. On the iPhone, you can even make emergency calls. Yes, the Lock screen can be secure or it can be convenient, it's entirely up to you!