How are pins used with this shield? The tutorial says that the header pins are inserted into the Arduino but the guide says they are not used for signals. Is there any way of using the other pins?
What it means is although all pins from the Arduino are connected only A4, A5 5V and Gnd are actually used by the shield. I think that these 4 pins are shared with other shields and all the rest of the pins are available for shields to either share or use exclusively.
So, if you have this shield and an Ethernet shield, which needs exclusive access to pins d7, d8 and d9 then you would be to use both shields at the same time.