Phase angle in harmonic oscillators represents the initial position of the oscillator relative to its equilibrium position, often visualized as a point on a reference circle. It is measured in radians and indicates the fraction of the oscillation completed at a given moment. The phase angle is distinct from angular frequency, which describes how quickly the oscillator moves through its cycle. Phase difference refers to the angular difference between two oscillators or points in the same oscillator. Understanding these concepts is crucial for analyzing oscillatory motion, including applications in electricity and wave mechanics.