The Arduino Mega Has Many More I/O Pins (54 Digital Pins And 16 Analog Pins)Than A Standard Arduino. This Shield Also Has Connectors Specifically For Some External Devices Like An Sd Card, Radio Communications (Bluetooth And Others).
It Also Has An Option To Power The "V" Pins On All The Digital I/O 3-Pin Groups From An External Power Supply Instead Of The Arduino +5v. This Is Good For Large Numbers Of Servos Etc.
The "Analog" 3-Pin Groups Still Use The Arduino +5v Which Is Better From An Electrical Noise Perspective. Version Has Two Options Of +5v Supply To All The "V" Pins jumper On: +5 Comes From The Arduino. Should Be Limited To About 300 Ma Jumper Off: +5 (Or Other Appropriate Voltage) Comes From An External Supply Connected To The Blue Terminal Strip. External Power Ground Must Also Be Connected To The Blue Terminal Strip.