What's VDC..?
 

is it traction control?

No, it is the Vehicle Dynamic Control which is more or less like stability control.

Isnt it the same thing as traction control really

When you lose traction VDC decreases engine power to bring the car under control (and probably also does other things)

It's actually much more than just traction control. It also incorportates a system to control each idividual wheel which can be braked or allowed to freewheel individually, as opposed to just controlling engine output due to loss of traction.
It's a very complex and effective system, which can help you a lot especially in wet conditions. :)
C.

and all the G35 has this feature or optional?

Standard equipement on the G's , M's, and Q's. :)
C.