A cadence is a final ending to a musical section. A climax is a high point of intensity. Harmony is the relation of notes to notes and chords to chords as they are played simultaneously. Melodic intervals are those that are linear and occur in sequence, while harmonic intervals are sounded at the same time. Whether or not a harmony is pleasing is a matter of personal taste, as there are consonant and dissonant harmonies, both of which are pleasing to the ears of some and not others.
Chords have meaning as they lead to other chords.
Certain progressions are encouraged as acceptable in certain styles of music. A triad is the most common chord form. A triad built on the second note of the scale is written as ii. The I chord is named the Tonic, and the IV chord is called by the name Sub-Dominant. The V chord is the dominant.