From what you describe, in Studio One, you are recording to a "stereo" audio track. A stereo audio track will look to record from 2 input channels at the same time. 1 input will be a discrete Left signal and the 2nd input will be the discrete Right signal. You record to a "stereo" audio track when you want to record a device that has a Left and a Right output. Like a keyboard.
A "mono" audio track will record from only 1 input channel. It will record a single wave on that audio track. This is then mixed to the outputs of your AudioBox which of course is a "stereo" Left and Right Output. Device Outputs are often Left and Right stereo, but device Inputs are different depending on the audio source/device you connect.
A microphone is a "mono" audio source. You will connect this to a single input channel and record this to a "mono" audio track.
A keyboard is a "stereo" audio source. You will connect this to 2 input channels and record this to a "stereo" audio track.