It may shake up or down or from side to side. The shaking can be felt if you touch a vibrating object. Some vibrations may also be heard - all musical instruments work by vibrations.

A simple way to see and hear a vibrating object is to take a ruler and put one end over the edge of a table. If you push the ruler down a little and then let go the ruler will vibrate up and down quickly and make a rattling sound. An electric buzzer vibrates when a current of electricity flows through it.