The two-slit experiment is a very popular and widely discussed example of quantum interference. Interference is a key attribute of quantum matter as a result of quantum phase and also a very common phenomenon of classical waves. However, most common experience outside of rainbows does not show quantum phase outcomes such as interference, coherence, correlation, nonlocality, or entanglement. The double slit experiment is one particular outcome that does show the diffraction pattern of quantum phase interference and nonlocality for quantum particles.
An electron is just such a quantum particle and an electron has both mass as well as the matter oscillations of quantum phase. As a result, a quantum electron has the two dimensions of amplitude and phase as its matter spectrum. A classical electron has just mass as momentum and there is no classical meaning for the matter oscillations of quantum phase. Therefore, a classical electron does not have a matter spectrum.
Here is an electron diffraction outcome from Bach, et al., 2013, that shows each of many thousands of electron outcomes of 600eV electron precursors passing through a double slit. The slits are each 50 nm wide and 280 nm apart and the 600 eV quantum electron has a radius of 50 nm. The classical electron has a charge radius of 2.8e-6 nm and so classical electron precursors would just show two ballistic patterns. In fact, a single slit apparently shows a ballistic pattern but in fact, even a single slit shows an interference pattern for quantum electrons. A higher resolution experiment will also show single slit diffraction and in fact, there is never really a classical electron.