The DC to AC inverter is located at the last stage of the solar power system. It’s job is to convert the DC (direct current) energy from your battery bank into AC (alternating current) energy that is used in the typical home.
'DC' refers to direct current, and 'AC' refers to alternating current. 'AC' is what is generated in electrical utility power plants and sent to homes to power appliances, etc.
You will need this inverter unless you have special appliances and lighting to operate on DC power that’s the same as your battery bank voltage.
Today's modern inverters can be very efficient, so very little power is lost during the conversion process assuming you’ve purchased a quality unit. This too is a part of the system that requires research.
A good DC to AC inverter provide pure sine wave AC power and will not damage your appliances (or electronics).