An inverter turns DC battery power into 240V AC power, the type used by normal Australian mains appliances. A pure sine wave inverter produces a smooth AC waveform similar to grid power.
That matters because not every appliance responds well to rougher inverter output. Modified sine wave inverters can work with simple resistive loads, but motors, compressors, chargers, medical devices, control boards and digital electronics may run hotter, noisier or less reliably.
A pure sine wave inverter is the safer choice when the load matters. Fridges, laptops, camera chargers, variable-speed tools, pumps and workshop equipment are all better served by clean AC output.
The key rating to check is continuous power, not just the highest number on the label. The inverter needs enough continuous output for the equipment being used, plus enough surge capacity for startup loads.
For vehicle and off-grid power systems, pure sine wave is the practical standard because it avoids unnecessary compatibility problems.