This document discusses phase differences between sinusoidal waveforms. It defines phase difference as an angular shift that occurs when two sinusoidal waveforms do not pass through zero at the same time. The document provides an example of a voltage waveform compared to a current waveform, noting that a phase difference of 30 degrees exists between them. Graphical representations are shown of waveforms that are in-phase with no difference and out-of-phase with a 30 degree phase difference between them.