The typical EU configuration:

The transformer delivers a neutral and three phases, in a star configuration.

That means you've got L1, L2, L3, N and GND.

N to any L is 230V, any L to any other L is 380V.

That also means a typical grounded socket has e.g., L1, N and GND, so a neutral and a hot.

A high-power socket or e.g. a stove will have GND, N, L1, L2, L3.

My stove has the oven running on L1 and N in a 230V hot/neutral and the stove at L2 and L3 in a 400V hot/hot configuration.

(Belgium is the exception, having phases at 113V off the center point, so sockets are in hot/hot to get 230V between the phases)

Here in the US, where split-phase is the residential standard, a house with three phase is quite rare. The HV lines running on poles in a neighborhood are mostly single phase, at least in rural areas like mine.

Yes! And many electrical devices rely on it, though sometimes fallback to regular 230V single-phase at 32A is possible, e.g. for stoves.

And considering a typical stove runs at 11-15kW and a typical electric water heater between 15kW to 25kW, you'll need it as otherwise you'll need far higher amps than is reasonable.

Honestly, only due to the technology connections video did I realize that the US does not use triphase power in most homes, which was genuinely surprising.

I have a friend with a Bridgeport vertical mill in his garage/workshop. He had to build a single phase to three phase converter, so he could run its three phase motors.