Fastboot is a protocol used to communicate with Android devices. It's a diagnostic tool that allows you to interact with your device's bootloader, which is the software responsible for loading the operating system. Fastboot is often used to flash custom images, such as recovery images, boot images, and kernel images, to your device. It's a powerful tool that's primarily used by developers and advanced users to modify and customize their devices.

If that fails, use the manufacturer’s official flash tool (Mi Flash Tool, Odin, or Android Flash Tool).

This 2,500+ word guide will break down everything you need to know about the fastboot unlock oem command, from basic terminology to step-by-step execution and troubleshooting.

When you toggle "OEM Unlocking" in Developer Options, you give yourself permission to eventually run the fastboot unlock oem command. The toggle itself doesn't unlock the bootloader; it merely tells the bootloader, “Hey, the user is authorized to run the unlock command.”