I do not know progression yet, and I really do not know what ii is
A chord progression is the series of chords that make up any given song.
Many songs, like "New Season", are based on a simple diatonic-scale-based chord progression.
Explaining it can be very involved but I'm going to keep it simple for now.
D major scale is:
D - E - F# - G - A - B - C# - D
The chords in the key of D will all be rooted on those notes in the scale but the chord voicings themselves will differ in sound (major, minor, diminished) based on the triad of notes that constructs the chords.
To keep it simple, the chords in the key of D would be:
D major - E minor - F# minor - G major - A major - B minor - C# diminished
Those chords are all assigned Roman numerals based on their relation to the root notes in the scale and their tonality (major = upper case and minor = lower case) as follows:
I - ii - iii - IV - V - vi - vii
So, a chord progression of IV - V - I in D would be:
G - A - D
The ii chord would be:
Em
Please understand that this is chord theory 101 in it's most simplistic form and there's so much more to it than this.
