A faraday wave happens when you shake a liquid back and forth very quickly. Imagine if you were shaking a big bowl of jello really hard. When you shake it, you might notice little ripples forming on top of the jello. These ripples are called faraday waves.
The reason this happens is because when you shake the bowl of jello, the jello starts to move around. But some parts of the jello are moving faster than others, so the jello starts to change shape a little bit.
When this happens, gravity pulls the jello down in certain places while the momentum of the jello pulls it up in other places. This back and forth motion creates waves on the surface of the jello.
Scientists like to study faraday waves because they can teach us a lot about how liquids move and behave. Plus they're pretty cool to look at!