Single phase power supply is common in approximately 85% of domestic UK properties. Simply put, it is where power to your home is delivered down one live wire protected by one fuse normally 60, 80 or 100 amps.
If you have single phase power, then the highest rate of charge you can get from an EV charger is 7.3kW (kilowatts).
The main difference between single phase and 3-phase is the amount of power that can be delivered. A 3-phase supply can typically deliver three times the power a single phase can, meaning 3-phase can offer up to 22kW charging if your EV supports it.