The household power supply is all three-phase five-wire system. That is, three phase wires (electrical symbols: A, B, C. cable color: yellow, green, red), one neutral wire (electrical symbol: N. cable color: blue), one ground wire (cable color : Yellow-green).
Single phase is any one of the three phases and a neutral. It is often called "fire line (phase line)" and "zero line". Usually refers to 220V, 50Hz alternating current. It is also called "phase voltage" in single-phase voltage electrical engineering.
Two-phase is to take any two of the three phases, and the voltage between them is 380v. Two-phase voltage electrical engineering is also called "line voltage".
Three-phase is to use all three phases. Three-phase electricity is mainly used as the power source of the motor, that is, the load that needs to rotate. Because the three-phase difference of the three-phase electricity is 120 degrees. The rotor will not be stuck.