Pure Sine Wave

Pure sinewave is a term used in inverter technology to indicate that an inverter outputs a waveform that is close enough to a real sinewave that electrical equipment will work without any side effects from being run off an inverter.

Marketing nonsense aside even a 'pure sine wave' inverter does not use a pure sinewave but a very good approximation of a sinewave, the bigger the number of steps (and the smaller the individual steps) the better the waveform will approach the ideal sinewave shape.