Tones are the basic elements of music. With the term "tone", one, single tone is meant. You have to distinguish tones from sounds, which are composed of more than one tone. The basis of all tones is, via a frequency, an exactly defined sinus tone. An instrumental tone, e.g. from a violin, is a complicated mixture of the (playing and sounding) basic tone and a couple of simultaneously occurring over tones. This fact, among others, is responsible for the typical sound of the instrument.