stereo/mono
what recording prgram are you using?
If you want a mono channel but it gives you stereo by default, you just have to change the track properties when creating the track.
As mentioned by farview, stereo tracks are usually used for things like drum overheads, where any signal processing (eq, compression) is going to be exactly the same for the two channels. It's just easier when mixing.
And I hope I'm not getting too basic here, but you asked what stereo and mono means.
A stereo track is two channels of audio, one on the left, one on the right (usually no extra panning is allowed or needed).
Mono is one channel that plays down the center or can panned left or right to any degree.