Waveform, or waveshape, is usually a graphical representation of a wave that can show its characteristics including frequency, amplitude, phase, duty cycle, and harmonics.
Frequency is the measurement of how many cycles per second a wave passes a fixed point. This is normally represented by Hertz, named after Heinrich Rudolf Hertz, who was the first to prove the existence of electromagnetic waves.
Amplitude is a measurement of the height of a wave, from the lower part called the trough, to the highest point called the peak. This is normally measured in volts.
Phase is a measurement of the period of time difference between one wave to another, and is measured from the same point in time. So wave X might have a phase difference of 30 microseconds from wave Y.
Duty cycle is the amount of time that a wave is on, or powered, compared to the time it is off, or not powered. A 50% duty cycle means that a wave is powered half the time.
Harmonics of a wave are waves that occur in multiples of the fundamental frequency. The fundamental frequency is the lowest frequency of a periodic waveform. A periodic waveform is a wave that passes a point in space per time period T. If T = 1 second, then the periodic waveform will have a frequency of 1 cycle per second, or 1 Hertz. And if the fundamental frequency is 1000 cycles per second, or 1 Kilohertz, then a third harmonic would be 3 times 1 kilohertz or 3 kilohertz (3,000 cycles per second).