What is meant by the words wave-particle dualism?

Basic physics questions: what is light and what is its nature? The difficulty of answering these questions is that when considering such phenomena as interference, diffraction, light manifests its wave nature. That is, these phenomena can be explained by assuming that light is an electromagnetic wave. At the same time, when emitting such phenomena as thermal radiation, photoelectric effect, it was found that light manifests itself as a stream of particles (copuscles or quanta). In this case, the properties of light are considered within the framework of the quantum theory of light. In classical physics, such a duality of properties, or, as they say, the duality of wave and corpuscular properties of light, cannot be explained.
The propagation of a wave and the movement of a particle in classical physics are considered completely different processes, and a wave and a particle are different physical objects, if only because the particle occupies a certain part of space (localized in space), we can talk about the size of the particle, its mass; a wave is a non-localized physical object, we can talk about the dimensions of space in which oscillations are observed, and these dimensions change in time. The similarity lies in the fact that both the wave and the particle carry energy.
A wave transfers energy from one point in space to another, but does not transfer mass, when the particle moves, the mass and, accordingly, the energy that it possesses is transferred.
Subsequently, it was found that dualism is inherent not only in light, but also in all microparticles. Wave properties have been found in electrons, neutrons, and so on.

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