Left and Right soundcard inputs

You're probably going to think this is a really stupid post lol, but I've asked a few mindlessly daft ones in the past anyway and got away with it. So here goes.

I always had the Left input on my soundcard for audio, and the corresponding Left audio output selected in the track output. I've now got a mixer, and I've got leads going from the 2 outputs (A channel goes to left, B channel goes to Right) on the mixer into Left and Right inputs on the soundcard.

But, because I've always got Left Audio selected as the audio track output, is the cable going into the Right input of the soundcard doing anything at all? When would I select the Stereo output in the audio track instead of the Left output?

I suppose I'm just asking when would I use the Right, and Stereo outputs on the audio track?

Yep, on nights tonight so when I get home in the morning I will try the Stereo output, with both Left and Right inputs used into the soundcard.

Generally speaking, Rob (Pulman), you don't want Stereo selected. The inputs are Mono. Recording them to a Stereo track only doubles the file size. Look at the waveforms on a stereo track recorded from your left input. They are identical, right?
Here'ssomething to try.
Record a track with your input set to Left. Hard pan the mixer balance to the left. Make sure this track is recorded as mono.
Now play it back, and move the panning slider from left to right.
Now record the same thing again, but this time, select stereo. Record to a stereo track.
Try the panning. pretty much the same, yes?
What's the difference?
Go to the Audio files in your project data. The stereo file is roughly 20Mb per minute, the Mono 10Mb per minute.
Same result, but you waste a lot of disk space recording a mono source to a stereo track.
The stereo option is mostly for the built-in sound cards, which will combine the seperate left and right inputs as a true stereo input.
However, in this case, if your input is on the left, and you record as stereo, the pan control will act more like a fader, with full volume on the left side and nothing on the right.
Hope that makes sense.

rob.pulman, what are you recording?
When recording like sounds from your hardware synth it might make sense to use stereo.