The double slit experiment is an experiment in physics that helps us understand how light and matter behave. It's called the "double slit" experiment because it uses two small openings, or "slits," through which light can pass.

When light is shone through the two slits, it creates a pattern on a screen behind the slits. The pattern looks like a series of light and dark bands, and is called an "interference pattern."

Interference pattern is caused by light waves passing through the two slits and then overlapping each other on the screen. The overlapping of the waves causes some areas of the screen to have a bright light (called constructive interference) and other areas to have a dim light (called destructive interference).

This helps us understand that light behaves both as a wave and as a particle, which is known as wave-particle duality.

It's interesting science experiment to observe, but it can be quite complex to understand, even for adults. But the basic principle is that, light can go through multiple paths, and when it reaches a destination the waves of those multiple path creates a pattern.