From man time:
The default format string is
%Uuser %Ssystem %Eelapsed %PCPU (%Xtext+%Ddata %Mmax)k
%Iinputs+%Ooutputs (%Fmajor+%Rminor)pagefaults %Wswaps
%E Elapsed real time (in [hours:]minutes:seconds).
%e (Not in tcsh.) Elapsed real time (in seconds).
%S Total number of CPU-seconds that the process spent in kernel
%U Total number of CPU-seconds that the process spent in user mode.
%P Percentage of the CPU
so real is the time that elapsed while the process was running
user is how much CPU-time it spent in user mode
sys is how much CPU-time it spent in kernel mode