A beginning violin player sounds very different than a violin player in a symphony, even if they are playing the same note. A violin also sounds different than a flute playing the same pitch. This is because they have a different tone , or sound quality. When a source vibrates, it actually vibrates with many frequencies at the same time. Each of those frequencies produces a wave.
Sound quality depends on the combination of different frequencies of sound waves.
Imagine a guitar string, tightly stretched. If we strum it, the energy from our finger is transferred to the string, causing it to vibrate. When the whole string vibrates, we hear the lowest pitch. This pitch is called the fundamental. Remember, the fundamental is really only one of many pitches that the string is producing.