The question is, what is the sound source?
An Audio track: Plays back audio files...
i.e. recorded audio files.
You can record audio from a microphone or audio input on to an Audio Track.
A blue apple loop is known as an 'Audio Apple Loop'. This has audio waveform data only.... just like when you play a CD, the file on the CD is in an audio waveform format.
A Software Instrument track: This type of track cannot play back audio files directly. In fact, it NEEDS a sound source or an instrument in the computer (inside Logic) to create a sound.
Logic comes with many 'virtual instruments' that create sounds.
In order to trigger these sounds MIDI notes are used.
Green Apple loops (Software Instrument APple Loops -SIAL) contain instrument settings, effects and MIDI note data. This data triggers the virtual instrument on the track to create sound.
.... So, yes, both SI and audio tracks output sound that we hear... but it's the input or source of the sound that make a difference.
Hope that makes sense.
Thanks for the invite and the CD offer. That's very kind of you!