Shield plays a role of intermediator between sensors and end user. It reads the values from sensors and display it on LCD possibly save them on SD card. Shield has eight RJ connectors: 3 analog, 4 digital and one for I2C communication. All sensors are connected to this connectros (for more look at Sensuino).
RJ connectros are 4-pin (4P-4C). Every digital connectro linked with two digital pins on arduino, +5V and GND. Every analog connectors is linked with one analog pin on arduina, +5V, VIN pin and GND. I2C connector is linked with SDA pin(A4), SCL pin (A5), +5V and GND. Supplying +5V for analog pins is stabilized with external voltage stabilizer on Sensuino shield. LCD and SD are linked with arduino by SPI interface. All four buttons are connected to one analog pin on arduino (look at menu).