Current mirror with source resistance
If parts are all perfectly matched:
Voltage on Rs on the left is R x 2 milliamps.
Vgs on the left is the voltage that corresponds to Id of 2 milliamps.
The voltages on both gates are the same (they are tied together).
Vgs on the right is the same as Vgs on the left.
Id is the same.

In real life there would be some mismatch.