A Sawtooth Wave or Ramp Wave is a single or periodic oscillation with a linear rise and a short linear fall. The period of a sawtooth signal is equal to the time from the sawtooth rise and the sawtooth fall.
A sawtooth signal is a harmonic-containing signal with even and odd harmonics whose amplitude is equal to the quotient of the harmonics. Thus, the 2nd harmonic has an amplitude half the amplitude of the fundamental, i.e. 1/2, the amplitude of the 3rd harmonic is 1/3, that of the 4th 1/4, etc.
Sawtooth oscillations are generated by function generators for test and measurement purposes. They occur wherever a time linear signal waveform is used. For example, typically in monitors for horizontal and vertical deflection.