Differing Purposes of the Standards.

The primary aim of the ISO 9000 standards is defined in the "Scope" section of ISO 9001:". . . specifies quality-system requirements for use where a supplier's capability to design and supply conforming product needs to be demonstrated."
The standards' primary purpose is, therefore, to provide a management model suitable for the supply of a conforming product or service between two parties -- a supplier and his customer. However, the focus on the use of the ISO 9000 standards as two-party models has shifted greatly as more and more use is made of them for third-party certification purposes. In today's complex world, there are limited opportunities for all customers to have direct relationships with their suppliers, so third-party certification bodies are, in effect, taking on the roles of representatives of multiple second parties (all the customers which rely on independent certification for their reassurance about a supplier). It is important, therefore, that users of third-party certification understand what form of reassurance is provided when an organization is certified against a quality system standard.
Since the ISO 9000 standards are generic, it is often a significant challenge to interpret their use in different industry sectors, or in organizations of different sizes or technical complexities. Quality system certification does not, however, certify the quality of a particular product or service for compliance with specific technical specifications, but only the management system's compliance with a defined model (ISO 9001, 9002, or 9003).