Explanation:

* The auditee is the organization or part of it that is subject to the audit. The auditee could be internal or external to the audit client . The auditee should cooperate with the audit team and provide them with access to relevant information, documents, records, personnel, and facilities .
* The audit client is the organization or person that requests an audit. The audit client could be internal or external to the auditee . The audit client should define the audit objectives, scope, criteria, and programme, and appoint the audit team leader .
* The technical expert is a person who provides specific knowledge or expertise relating to the organization, activity, process, product, service, or discipline to be audited. The technical expert could be internal or external to the audit team . The technical expert should support the audit team in collecting and evaluating audit evidence, but should not act as an auditor .
* The observer is a person who accompanies the audit team but does not act as an auditor. The observer could be internal or external to the audit team . The observer should observe the audit activities without interfering or influencing them, unless agreed otherwise by the audit team leader and the auditee .
References :=
* [ISO 19011:2022 Guidelines for auditing management systems]
* [ISO/IEC 17021-1:2022 Conformity assessment - Requirements for bodies providing audit and certification of management systems - Part 1: Requirements]