Turnabout

what does "turnabout is fair play" mean?
thanks in advance!

I don't know, but the internet does.
From dictionary.cambridge.org

Turnabout is fair play. American
something that you say which means you will do something that someone else has done because this is fair
You cook dinner tonight, I cooked last night. Turnabout is fair play.
(from Cambridge International Dictionary of Idioms)

Here's what one reference says:

TURNABOUT IS FAIR PLAY - "We should do this by turns; each of us should have some time in this good or bad situation. 'Turnabout' is an old noun meaning for two people to do something alternately or by turns, and the saying dates at least to 1755, when it appeared in 'The Life of Capt. Dudley Bradstreet.'" From The Dictionary of Cliches by James Rogers (Ballantine Books, New York, 1985).

I guess I'm mixing this expression up with "what goes around, comes around." If you do something bad, then bad will be done to you.