GoKawiilQuick Start is one of those "magical" Apple features. Just turn on your new iPhone next to your old one, confirm you want to use your Apple ID for setup, and Quick Start takes it from there. Your old iPhone shows an animation on the new one for you to scan with its camera. That's what pairs the two devices and kicks off the transfer.
Now you'll go through some basic iPhone setup steps, such as entering your current passcode and setting up Face ID or Touch ID. When your new iPhone asks how you want to proceed, choose your most recent iCloud backup or transfer everything from your old iPhone using direct transfer.
Are you in a hurry to start using your new phone? Choosing iCloud is your best option, since it downloads the essentials first and does the rest in the background. but it takes much longer when you have a lot of photos, videos and more on your old phone. iCloud is usually the fastest option, especially when you have a good Wi-Fi connection available.