It can be confusing when so many parts are discussed. If you just remember that solar inverters give you the ability to take the power created by the solar panels and use it to power your home, it becomes more clear.
A solar inverter turns inefficient DC power to stable 120 volts AC that most appliances run on. Solar inverters can be used in off the grid applications to charge batteries. They can be used as grid tie inverters to send extra power created back into the utility line. They can be used as backup to manage power from batteries to your home in a power outage just as a fuel powered generator would but without the fumes or extra cost. The solar inverter is critical in having a solar energy system.