To put it simply, different systems have different data layouts. Each system has “entry points” based on the data. Usually we do one-to-one connections, but now we can bend the data and execute multiple flows.
Essentially, it means that you don't need to delete your data in either system. We're able to push products through without creating duplicates, as long as each product has its own SKU and they are matched correctly between the systems.
This will make it easier in the future to integrate systems that traditionally have been difficult to integrate. For example, Revel, Unleashed, and Magento systems do not allow for product variations, meaning each product variation has to have it's own SKU. But Shopify and WooCommerce allow one product with different variations to be grouped into one SKU. This previously would create problems in connecting the systems. But with mass sync there will be more ease in the process, so long as every product is considered a simple product with its own SKU.