Amazon FBA means "Fulfilled by Amazon". This business model allows anyone to leverage Amazon's network, workers, warehouses, facilities, and customers to make a passive income as a certifies FBA Marketplace Seller.
In essence, you find a product already in demand, find a supplier or manufacturer, send it to Amazon Fulfillment Center, sit back and watch those profits come in,
When someone places an order for your product, Amazon will package, ship, and deliver that product to the doorsteps of their customers.
That means that FBA sellers don't need to deal with fulfillment, handling inventory, or customer service