A vibration is a shaking motion. If you feel a strong vibration in your car every time you step on the brakes, it might be a good idea to take it to a mechanic.
You might feel a vibration in your floor when your neighbor is playing his music too loudly, and you'll know a thunderstorm is approaching when you feel the vibration of your trembling dog at your side. The rapid back and forth movement or quivering of an electric toothbrush or a mild earthquake is a vibration. The Latin vibratus, "move quickly to and fro" is the root word.