Elapsed time and execution time

What do those metrics really mean?
In the documentation is written :
metrics.elapsedTime = The total time taken for the request, that is the time from when the request was received until the results were returned.
metrics.executionTime =The time taken for the execution of the request, that is the time from when query execution started until the results were returned.
but what exactly does it means?
Is the executionTime the same as the CPU time in Oracle?
Is the difference between the elapsedTime and the executionTime the time it took to the query server to start executing the query? In which cases this delay of starting executing a query could be high?

Thanks!

Hello,

When the request arrives at the server, it is placed into a queue until a worker thread picks it up. Elapsed time includes time spent in the queue, whereas execution time does not. They are both wall clock times, not CPU times.