Symmetric input

[Garoll]

I would like to ask you what it is meant by "symmetric input" in the instrumentational amplifier schematics and in the differential amplifier? I can`t understand what is the difference between symmetric and non symmetric input and output as parameters. Can anyone explain ?

Thanks

[Bob S]

I would like to ask you what it is meant by "symmetric input" in the instrumentational amplifier schematics and in the differential amplifier? I can`t understand what is the difference between symmetric and non symmetric input and output as parameters. Can anyone explain ?
Probably they mean a balanced diferential input, like

Vplus = A·sin(ωt), and

Vminus = -A·sin(ωt)

Bob S