what does differential input voltage mean

So if i have differential input voltage vi and -vi, does the differential voltage mean 2vi and the differential voltage amplide is mag(2vi)?

Hi.
In the differential amplifier, the voltage that be amplified is differential input voltage. if one input is Vi and Other is -Vi, then the voltage in the output is
Vo=Ad*(2Vi). that Ad is differential gain in the differential amplifier.
regards.