It depends on your countries regulations, if any.
Here, in NA, we get what's called SINGLE phase into our house. Don't let that fool you.. it's really 2 phases 180 degrees apart. (each phase is 120V 60Hz)
There's a lot of other countries that deliver 'SINGLE' phase 240V 50Hz..
That means only ONE leg is power..
Then, there are 3Phase, 120 degrees 240V Countries..
Industrial power here in NA is normally 3 Phase 120V 120Degrees...
Too bad we can't just 'all agree'