Gestalt psychology is a perceptual psychology discipline that was developed in the early 20th century, including by Wertheimer.
Gestalt psychology describes elementary perceptions as so-called gestalts.
Wertheimer classified different types of gestalts and derived so-called gestalt laws or gestalt principles from them. This classification is still recognized in practice by media professionals today, though it has also been greatly expanded and modified.
Gestalt psychology follows a tradition of psychology based on introspection. It is not considered empirically verified. To reflect the hypothetical status of Gestalt psychology, gestalt laws are referred to as gestalt principles in modern sources.
Source
Wertheimer, Max (1923): “Untersuchungen zur Lehre von der Gestalt” (Investigations into the Teaching of Gestalt). In: Psychologische Forschung. Journal of Psychology and its Border Sciences. Vol. 4. Koffka, K. [et al.]. Berlin: Springer. pp. 301-350