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GSR, standing for galvanic skin...
The Uno is a microcontroller board based on the ATmega328P.
The Mega 2560 is a microcontroller board based on the ATmega2560
The Motor Shield is a driver module for motors that allows you to use Arduino to control the working speed and direction of the motor.
Mega Shield is a extension board for Arduino Mega and Google ADK.
As an expansion board, Base Shield v2 has many Grove connectors, making it convenient for you to use Grove products together. And It is compatible with a series of Arduino products.