Audit trail

"Do you have a definition and any examples of an "audit trial" used for ISO compliance?"
 

Answer:

I am sorry but this term is not used by ISO 27001, so it is not necessary for ISO 27001 compliance. Anyway, I suppose that you mean “Audit trail” that in information security means a chronological record of system activities to enable the reconstruction and examination of the sequence of events and/or changes in an event (Definition from Wikipedia), which is more related with forensic activities.
Audit trail is also a technique that an auditor can use in the internal and certification audit, but again, it is not necessary for the compliance of ISO 27001. An example: During the audit the auditor finds that certain system does not function properly - related to this issue he has found that people operating that system are not trained for using it, and they are not trained because HR department didn't receive enough funding. Therefore, the audit trail has followed three different activities in a company, and all of them are very closely re lated. 
If you are interested in how to perform an internal audit, this article can be interesting for you : “How to make an Internal Audit checklist for ISO 27001 / ISO 22301” : https://advisera.com/27001academy/knowledgebase/how-to-make-an-internal-audit-checklist-for-iso-27001-iso-22301/
And finally, if you need more information about ISO 27001, please read this article “What is ISO 27001?” : https://advisera.com/27001academy/what-is-iso-27001/