Audit trail
In one sentenceA record the system keeps of every operation: who added, edited or deleted it, when, and what the value was before and after the change.
Simply put
The audit trail is the system's memory: if an item's price changes or an invoice is deleted, you know who did it and when, instead of guessing.
The external auditor relies on it to test how reliable the figures are, it protects the honest employee from accusation, and it reveals manipulation early. That is why an ordinary user must not be able to edit or delete it.
Example
At the stock count a shortage appears in an expensive item. Checking the audit trail shows that a sales return was recorded on it three times after the shift was closed, by a specific user, so you know where to start checking.
Don't confuse it with
General ledgerThe general ledger shows journal entries and account balances, and the audit trail shows who entered each change and when.