The bootloader mode is the first and possibly the most important part of the Android OS. The loader, as the name implies, loads the boot image, scans the entire system for errors and custom parts. Some of them can be corrected without user intervention, and some require attention.
When you boot a device in the bootloader mode it gives you the opportunity to choose where system will go:
- Recovery mode
- Fastboot mode
- Other modes
And now is the main question: “Why you need to know what is bootloader mode and why is it neccessary to unlock it?”. As I said earlier, bootloader scan system for a custom software, so if you want to install any custom rom or even custom recovery – you need to disable this check, or device will not boot, or will be factory reseted.
To disable bootloader check, you just need to unlock it. Be careful, the unlocked bootloader can lead to a loss of warranty!