A cause is the most direct reason that something failed. For an example if an employee loses an unsecured laptop filled with confidential data, the cause may be labeled as human error.
A root cause required analysis that looks at fundamental reasons that a failure occurred. This consider deeper issues such as processes, systems, design and chain events.
In the above example root cause may be that laptop wasn't encrypted properly.
When a identified cause breaks the chain of asking why and mitigate the risk then a cause is termed as root cause