User CPU time vs System CPU time?

Could you explain more about "user CPU time" and "system CPU time"? I have read a lot, but I couldn't understand it well.

Solution 1:

The difference is whether the time is spent in user space or kernel space. User CPU time is time spent on the processor running your program's code (or code in libraries); system CPU time is the time spent running code in the operating system kernel on behalf of your program.

Solution 2:

User CPU Time: Amount of time the processor worked on the specific program.

System CPU Time: Amount of time the processor worked on operating system's functions connected to that specific program.