Groups are two or more notes played at once. They are closely related to scales, they’re different in that the notes have more space between them.

Scale would be like c, d, e, f, g, a, b

Chord would be like c, e, g, b

Those are the c major scale and c major chord. If you hear the chord, you can play the scale or you can play the notes more like the chord as something more like an arpeggio. An arpeggio is a chord that is played one note at a time.

With one saxophone, you can’t play a chord. But you can play part of a chord. A piano or guitar can play a full chord on their own.