Back lit just means the Screen is using built in light diodes to illuminate the screen further.
In simpler terms let me explain it in general public understanding LCD and LED TV's now we all know LED is back lit, but what most of you don't know is LCD, CRT is also back lit... I mean how else can the image project?
So for you to understand this is what you need to know: Do you like it very bright or just kind of bright?
The back lit will assist you when working outside in the sun, when the sun is shining on the LCD screen it will create glare, the back lit will help to balance that glare slightly because the sun will still overpower it however because the light is now stronger you can see a better image than before.
If however you are just working inside and there will not be any glare on the screen it's not needed.
It all comes down to how you will use the camera and personal preference...
I don't use it, you might love it...