Important Question about CST

A CST question: How can I use time domain solver to get S11 frequency response? I read in the manual that we can do that by Transient Simulator "Broadband calculation of S-parameters from one single calculation run by applying DFT?s to time signals" but i don't understand what does that mean?

Can someone help?

Actually, CST computes the FFT of the input/output signals and automatically reports the S11.