First things first :-
1. What is bootloader?
> Bootloader is a piece of code that runs before android loads up. Bootloaders usually contain several ways to boot the OS kernel and also contain commands for debugging and/or modifying the kernel environment.
2. Benefits of unlocking bootloader?
> You can flash custom kernels/ROMs.
> You can ALWAYS root your device. (compelling, eh?)
> You can flash alpha builds of newer firmware ( generally newer android version ) which is under testing and not meant for end consumers.
3. Disadvantages of unlocking bootloader?
> You may void your warranty.
> You may loose some proprietary vendor software such as Bravia Engine, Download Music info etc. due to removal of DRM security keys.
> OTA updater may refuse to update your device and pop up a 'Device's software modified' message.
4. Can i unlock my bootloader?
> Go to dialer
> Type *#*#7378423#*#*
> Service info > Configuration
> Rooting status :
"Bootloader unlock allowed" - You can unlock your bootloader
"Bootloader unlock not allowed" - You cannot unlock your bootloader
You can unlock bootloader in two ways:
1. Official way(Instructions Included)
1. Generate your unlock key by entering your IMEI. (To check your IMEI - *#06# )
2. After you have the key, use flashtool or cmd prompt to unlock. (easy?)
3. To verify, check rooting status :
"Bootloader unlock done" - Congrats, you've successfully unlocked your bootloader.