A true sine wave inverter will convert the power produced by your vehicle in a true sine wave. This allows for a cleaner power output with less distortion and will allow larger items like appliances to run cooler and quieter. A modified since wave inverter will not convert the power from your car and are typically only suited for smaller items such as fans or lights. If you're planning on hooking up items such as laptops/computers, game consoles or appliances, you want to use a true sine wave inverter.