Bryan,
Its terminology that you don't HAVE to understand in order to play. In a nutshell:

The C major scale is C, D, E, F, G, A, B and the next note, C starts a new octave. Notice it is only a half step from the last note in the scale to the new octave. The G scale is G, A, B, C, D, E, F# and the next note is G. Every note in the G scale is also in the C scale except the F#. On an accordion, you have to use the notes that is there which is an F (F# flattened a half step). The seventh note is flatted making it a blue note; however the only TRUE blue note is a flatted fifth which can only be attained when playing in F. In that case, you lose the fourth. It gets even deeper.

I would just listen to a lot of music and play.

Talking of blues notes, can anybody suggest some simple blues tune I cold try in position 1 or 2

cheers

bob

Drunkards Blues is a good one to try.