What is the UPS function on the LF inverter?

When use UPS function, the inverter should have battery connected on the DC input side, and the home grid connected on the AC input side, home grid has power, the led light marked " BTY ON" will be on, it will charge the battery. When the home grid power is off, the inverter function will be work, the led light marked "INV ON" will be on, the battery charger function will turn on automatically when the ac input is restored following an ac power failure.