What is Mono (single) and what is Stereo (dual) used for? I'm guessing mono is something to do with one and stereo is something to do with two.. just because mono has single and stereo has dual.. haha.
If you are recording something with one mic or something with a single source, like a guitar plugged directly in, you would use a mono track.
If you are recording something like the stereo output of a keyboard, drum overheads, etc... you could either use a stereo track or two mono tracks panned wide.
You might want to look up the definitions of 'stereo' and 'monophonic' so you can get a handle on the concepts.