There are reports that Pixel phones sold via the Google store will be rootable and will also ship with an unlockable bootloader. Meaning, Google Pixel and Pixel XL owners can root their phones so that they can have a complete control over their devices. Once the phone is rooted, Pixel users can experiment a lot of things i.e. optimize or tweak your phone’s hardware settings, reduce the power consumption, etc. This is not surprising since the earlier Nexus phones all had an unlockable bootloader.
In other news, Pixel phones sold on Verizon will not have unlockable bootloaders. There is literally nothing users can do about it given the fact that carrier’s policies generally work this way. In addition to this, Verizon-exclusive units will also come with three applications that users cannot uninstall. While this may still be upsetting for few, Pixel phones sold on the Google store will have no room for such complaints as they ship with an unlockable bootloader. Updates pushed on Pixel phones sold via Verizon will be on par with Google updates.
The bootloader in a phone is what packages the mandatory set of instructions that boots the kernel. The Kernal is an instruction set that acts as a bridge between software and hardware resources. To root any Android device, it is mandatory to have an unlocked bootloader. This is how you will be able to install a custom ROM (modified version of Android OS) onto your device. If you want to know more on what is rooting or how to root an Android phone, this article on XDA Developers may help you.