When you feel something vibrate, it trembles and shakes. A mild earthquake, for example, might make your chandelier vibrate.
A hummingbird's wings vibrate, and so does an electric toothbrush. That extremely rapid back-and-forth movement is what happens when something vibrates. Something can also vibrate in a more musical, resonant way — the sound of an organ might vibrate through a church, for example. The root is the Latin word vibratus, which means "move quickly to and fro or shake."