What is an inverter used for

The purpose of inverter
An inverter can be simply known as a movable socket, you can connect your ac appliance to the socket as you connect at home. Inside the inverter, it has the transformer circuit can transfer dc to ac. So outside the inverter in the input part of the inverter, it needs to connect to the battery to get the dc power.

The function of inverter in solar system
The solar system is composed by the solar panel, solar charge controller, battery, inverter and other spare parts. It has two steps for power convention, The first step is dc to dc, the solar panel generated the PV power and pass through the solar charge controller which will be modified to be suitable dc power to charge the battery.
The second is dc to ac. The battery offer the DC power to the inverter as power source to connect the input part of the inverter, the dc power pass though the transformer and other modification circuit change to be AC power.