Device IO indicates which hardware input is associated with that software channel.
Gain In compensates for different input levels (mic or line), and should be set so Peak In flashes only occasionally (6dB headroom).
Phan Pwr assigns +48 Volt phantom power to the input for condenser microphones.
Mute In turns the input signal on/off.
Level In adjusts the relative input volume.
Invert In reverses the polarity of the input signal.
If standard Audia or AudiaSOLO hardware is being used, then stereo input summing is available on 12x4 configurations (see Fixed 12-Channel Input)