Hello,
may I ask the gurus a question please.

What does a SWR meter actually display?

effective power
reactive power
apparent power


What does it display in the 1 : 1 case with optimal impedance matching
between transmitter, cable and antenna, I guess it's effective power,
but what does it display when matching is off, say, 1 : 5
or even worse, when the mismatch SWR is 1 : 10 or greater?
There are two pointers in the instrument, forward and reverse,
how do they add up? Why do forward power and reverse power both
increase in their values when the antenna is strongly mismatched,
but the displayed SWR remains the same?

Please elaborate a little on the answers for a beginner like me.
Thank you,
w.