confusion over AD620

On working with AD620 instrumentation amplifier, i found that pin number 5 has been designated as REFERENCE...

what is this mean? wat should ideally be supplied to this pin?
i supplied two input signals of the same amplitude and frequency to the 2 inputs of the AD620... i was getting an amplified output... i should be getting almost zero output rite???

i am not able to understand why this is happeneing... can u ppl help me...

Have you reviewed the examples in the data sheet:

https://www.analog.com/UploadedFiles/Data_Sheets/37793330023930AD620_e.pdf

Unless used for a specific purpose, the Reference is connected to your power supply common. This is the same "common" used by your input and output signals.

Ken