When you strike, tap, etc. an object, you cause it to vibrate or cause it to move back and forth.
Sound uses matter as a medium to move from one place to another. It can travel through solids, liquids, and gases. It can travel best through solids because the particles are close to each other. Sound waves travel slowest through gases because the particles are furthest apart.
Sound can be described as having pitch and volume.
Sound is all around us. Different animals can hear different pitch sounds. Some can here lower frequencies and others like dolphins can here amazing high pitched sound.
Listening to sounds around us is just one way of describing the world around us. Enjoy!