Three phase as it sais on the tin has three 460V Ac phases, you can use one phase at 230v to ground. Trying to put it simply the voltage is alternating and the voltage between a single phase and ground is a maximum of 230V (what you see in a domestic set up) but as the next phase still has alternating Voltage but at a different time to the first power line the voltage between the two will see a max of 460V. Max V phase to ground is 230v max voltage phase to phase is 460, this allows bigger machines to use smaller cables as for a given motor power the current will be much smaller at 460v than at 230v.

Does that make sense? if you have three phase machines and you don't have a three phase supply you can get converters.