When an auditor performs an audit, he or she compares the reality with the audit criteria. If the reality is not according to the audit criteria, we have a Non-Conformity. If the reality is according to the audit criteria, we have a Conformity.
Even when the auditor identifies a Conformity he or she can also find, due to his experience, an Opportunity for Improvement. Some auditors also use word Observation.
Based on ISO 19011:2018 one can say that:
Non-Conformity – it is when an audit criteria, a requirement is not fulfilled
Conformity - it is when an audit criteria, a requirement is fulfilled
ISO 19011:2018 and ISO 9000:2015 do not have definitions either for Opportunity for Improvement or for Observations. Nevertheless ISO 19011:2018 states that the findings of an audit can lead to opportunities for improvement but onl y defines improvement. An activity to improve performance.
So, the evidence presented indicates that a requirement has been effectively implemented, but based on auditor experience and knowledge, the organization can take advantage of modifying its approach.