It’s amazingly transparent and impressive to see it work.
Even your “old” screen arrangement is duplicated.
If you have a new phone (replacing a lost or stolen phone) during the setup you’ll be asked if you want to restore from your iCloud backup.
Select “yes” and it’s off and running.
You’ll see all your data download, followed by re-installing of your apps.
Any cards in your wallet will reinstall as well, although you WILL have to re-enter each credit card’s security code.
IF you are “upgrading” and still possess your old phone, there’s a slightly different - and faster process outlined here:
Use Quick Start to transfer data to a new iPhone, iPad, or iPod touch - Apple Support