What's the dealio with them? I can't find any good sources that explain aside from their formula and how there are only a handful. Can anyone else point me to a good source of information about them?
its a dissonant chord that often acts as a dominant (leads to the tonic). It occurs as part of the harmonic and melodic minor chord scales on the 3rd degree
There was just a thread about Diminished and Augmented chords.