[R] Meaning of proc.time()

[Christofer Bogaso]

If I run proc.time() function, I would get following:

> proc.time()
   user  system elapsed
   2.82    4.18  792.39

However I am struggling the meaning of the object what it returned. In
help file it says that:

"user time" is the time required to execute the calling process. Here
what is the calling process exactly? Who executes this? system itself?

2ndly "system time" is the time required by the system for execution
of something.......... what execution? What is the meaning of " on
behalf of the
     calling process?"

3rdly what is elapsed time? Total time I spent on current session,
since I opened the R window?

Really sorry if I asked trivial questions, however honestly I could
not understand those. Some helpful comments are highly appreciated.

Thanks,