Of EVERYTHING. I really don't understand "diminished" or "sevenths" or ANYTHING when it comes to chords.. I know major and minor, and that's it. Is there an easy way to explain the chord layout?

Nor do I see how pentatonic scales are related by their notes. such as the A minor scale, etc..
Yes, they sound nice when put together, but how are they defined to be put together?
that's alot of reading to do, but i'll do anything to get this knowledge crammed into my head! thanks.