Your ERP is still the master
The webshop works on the same data as the rest of the Chainbox platform, and your ERP is the source of:
products and product data
customers
prices and price lists
discounts
sales orders
invoices and credit notes
other customer-specific information
Data is mirrored to the Chainbox platform, where the webshop can work fast without putting load on your ERP. How often, and how it works, depends on your ERP.