The 240 volts is for North American split phase residential usage.
Every house in north America has 240 Volts coming into it. We have two live lines and neutral. (Not Three phase.) Things like electric dryers, stoves, and water heaters use this to keep the wattage up, but the current in each conductor down.
You'll never see 3-phase in a residential building, unless your on a farm, and that's all that comes in from the road for the needs of the farm (like grain dryers and stuff), or 3-phase has been specially requested for some specific reason.
Cya,
Chris