WHAT EXACTLY IS FLASHING???

Flashing basically means changing the firmware(software) of your phone.Your phone firmware(software) is made up of two parts the Phone MAIN and the phone FS. Flashing allows you to change either or both parts of this software.Also Using program called FAR MAnager you can even change individual software driver files in any of the mentioned two parts ( i.e MAIN or FS).

Advantages of flashing are many:

The main one is the the stock K750i does not have the trademark "Walkman player" as the W series phones have, hence by flashing the K750 to the W800 software we can achieve this , so we end up with better acoustics(sound) thru the earphones and external speaker
By changing individual drivers we can change the software that governs the camera or display of the phone hence it is possible to fine tune them as you wish.
Happy flashing....