How do I record audio?

I have a Presonus AudioBox 22VSL interface and the accompanying software. It's the default device for playback and recording. I have a guitar plugged into it.

In BB when I hit Record Audio I get the VU meters and they work but nothing gets recorded. If something were being recorded, where would I find it? Where is the track, or file, or whatever you call it? Is that what I'm looking at when I hit Audio Edit? Is it possible to record more than one audio part, or track, or file, or whatever you call it? If so, is there any provision for mixing them?

Also, what does it mean to say "If you also want to record MIDI . . ." What MIDI, from where to where? Why would I be recording MIDI and audio at the same time? And where would the recording be found?