There are key parts to Android OS, the modem, bootloader and system. With Fastboot, you can easily flash certain parts of or a full system. Depending upon the manufacturer, there are different ways to access Fastboot mode - all of which have been listed in this detailed tutorial. Further, for enthusiasts, this acts as a portal towards installing new firmware updates manually as well as modifying the system partition.
This comes in handy for official repair technicians to restore system files if the phone is not booting up. Most, if not all, Android devices come with the bootloader mode. This way, once connection is established, you can flash system files directly onto your Android device - be it official firmware files, system updates or custom files such as a custom recovery i.e.
However, unlike recovery, to utilize Fastboot mode, you need to have your phone connected to a computer on which you have configured the Fastboot utility. Similar to Android’s recovery mode, Fastboot is another great built-in mode that lets users install and flash system files. This mode is also known as bootloader mode. Here is a detailed tutorial on how to access and enter Fastboot Mode on Android.
