Google made it easier to transfer your important data from your previous iPhone or Android device to your new Google Pixel phone. This feature is part of the phone setup process, and in the official website is files under a tab called Switch. In just three steps, all your important data will be automatically transferred to your new phone.
According to the official Google Pixel product page, the Switch functionality is supported for a limited amount of devices that meet these specifications as provides by Google: iPhone or iPad running iOS 8 and up, Nexus 5, 6, 5X, 6P running Android 5.0 and up, as well as most Android devices that run Android 5.0 and up.
No doubt that Google wants you to switch and has a great confidence in its brand new home-made smartphone. This migration tool really makes it easy to switch and bring your contacts, photos, videos, music collections, texts, calendar events and iMessages, all into your brand new Google Pixel device.
Just keep in mind that some of the data might not be automatically transferred. I would probably do a check after the process finishes just to make sure that I don't leave any important and private information behind, especially if I intend to sell my previous phone to another person and plan to reset my older phone completely and erasing all data from it.
The Switch feature is part of the Google Pixel setup process. You can continue the phone setup process while data is being transmitted to your new Pixel phone. You can also decide to skip it and do it later on.
All in all, it's a great feature to have that makes the migration painless and seamless.