> The other question is : is there anywhere specified to what the pins in the
> attached picture...
It almost looks like that may be for an alternate form factor (QFP) of the ICSP
(In Circuit Serial Programming?) MCU (PIC18, QFN) on the top side of the board.
> Where in the PIC32 starter kit 120 pins connector layout specified...
If you are referring to the 132 pin connector, it is documented on page 40 of
the PIC32MX Starter Kit User’s Guide at: http://ww1.microchip.com/downloads/en/DeviceDoc/PIC32_UsersGuide.pdf
There is a similar schematic for the USB version of the chip in its user's guide,
but beware -- many pins subtly change places/functions between the USB
and non-USB versions of the chip, not to mention between 64 pin and 100 pin
variants. (If you only look at the extension board schematics or pin names it
may be quite misleading.)
> Just another question, what is the definition of the J3 connector...
That is the ICSP connector which is how the PIC18 controls the PIC32 on your
Starter Board. Presumably, you could use that to control an off-board PIC32
as well (or maybe even to control the on-board PIC32 from an off-board ICSP).
If you have room for it and you want to play with the ICSP connectors for
programming/debugging it, you might also consider this board to break out all
the pins in a convenient form factor: http://www.sparkfun.com/commerce/product_info.php?products_id=8971