Here's how it works:

1. Setup: A beam of electrons is fired at a barrier with two narrow slits.

2. Expectation: If electrons were purely particles, you'd expect two bright bands on a screen behind the barrier, corresponding to the electrons passing through each slit.

3. Observation: Instead, what you observe is an interference pattern of alternating bright and dark bands. This pattern is characteristic of waves, as the crests and troughs of waves interfere with each other.

Why this is significant:

* Wave-particle duality: The double-slit experiment demonstrates the wave-particle duality of electrons (and other quantum particles). This means they exhibit both wave-like and particle-like properties depending on the experimental setup.

* Quantum nature of matter: This experiment is a fundamental pillar of quantum mechanics, proving that matter at the microscopic level behaves in a way that is fundamentally different from the classical, macroscopic world we experience.

Let me know if you'd like more details on how the interference pattern forms or any other aspect of the double-slit experiment!