A scalar is defined as a single numerical value, while a wave represents a repetitive variation of that value. The discussion highlights examples such as the altitude variations in Wisconsin and sound waves, where the intensity of sound can be viewed as a scalar that changes cyclically. This concept is linked to Electronic Voice Phenomenon (EVP) research, specifically referencing Tesla's work, suggesting a connection between scalar values and the analysis of sound and its variations in EVP studies. The conversation emphasizes the relationship between scalar quantities and wave phenomena in understanding complex audio signals.