Customers sit on the selling side of your business. For a manufacturer they may be distributors, retailers, dealers or direct business buyers. For a distributor they are the retailers, contractors and businesses it serves. Each customer relationship runs an order-to-cash process: order, acknowledgment, shipment notice, invoice and payment.
B2B customer EDI is common with large retailers and distributors, which often set their own document requirements and expect suppliers to meet them. Many other customers order by email, phone, spreadsheet or PDF, including large organizations that use EDI for some processes but not others. Every manual order has to be keyed, checked against pricing and terms, and tracked separately, which slows confirmation and invites errors.
Remember that customer is a role, not a company type. The distributor that buys from you is your customer, and it is also a supplier to the retailers it sells to. Clean customer data, accurate pricing and timely status updates are what customers experience as good service.