The ISO 9000 family of quality management systems (QMS) is a set of standards that helps organizations ensure they meet customer and other stakeholder needs within statutory and regulatory requirements related to a product or service. ISO 9000 deals with the fundamentals of QMS, including the seven quality management principles that underlie the family of standards. ISO 9001 deals with the requirements that organizations wishing to meet the standard must fulfill.
ISO 9001 certification has a three-year validity period. At the end of this period, every certified organization must renew its certificate. Unfortunately, not all organizations are successful in their renewal. Some organizations are not able to renew the certificate, because they do not conform to all requirements, and others simply decide not to renew the certificate.
More information, visit https://en.wikipedia.org/wiki/ISO_9000