Meaning of Elap per Exec (s) -

I think we face some problems with the performace of our DB.

We have quite good execution times seen in AWR reports 

So what is the Meaning of Elap per Exec (s)  ---it is the time the result of the sql reach the client ? 

I read this document How to Identify Resource Intensive SQL to Tune [ID 232443.1]

where it is defined Response Time = Service Time + Wait Time

Is the response time = elapsed time (s) ?  or is only part of the Service Time

Thanks