8. Chord Symbol Notation

Understanding the chord notation can be very useful if your looking at chord charts, but can also develop how you think about using chords.

Major and Augmented chords are always capital roman numerals.
Minor and Diminished are always lower case.
Any additional symbols such as "+" or "°" or "maj7" will appear in the superscript above the number.
Chord symbols don't identify if the 2, 3, 6, or 7 chords are rooted on major or minor intervals, they assume you know which notes belong in the scale you're using.

If you were reading a chord chart for a song in a major key, you would then expect to see I, ii, iii, IV, V, vi, and vii°, because of the pattern the diatonic chords follow in a major scale.
If you came across a "II", that would mean to play a major chord where the 2 falls on that scale. If we were in C major, that would mean playing Dmaj instead of Dmin.
If you came across a symbol that said "bii" that would mean play a minor chord half a step below where the 2 is supposed to be in the scale. In C major, that would mean Dbmin. The same concept would apply if you saw a sharp symbol on a chord symbol. It's very common to see a "bVII" used with a major scale. It sounds awesome even though its out of key.