This guide is only valid for Sony Xperia E3 and Sony Xperia E3 Dual only. And this guide has been completely tested and succeeded with Sony Xperia E3 Dual (D2212).

What is meant by Unlocking Boot Loader? When a computer starts up you can press a button like F2/F8/ESC key and enter to the BIOS menu (Boot menu). This is also a some kind of boot loader. For another example, if you have installed multiple operating systems in a single computer then a menu will be displayed at startup asking which OS to boot. This is also called a boot loader. In Android phones there is a similar boot menu. But this menu has been locked by default.