what is it?

A squawk code is a code that is given to you by ATC to key into your transponder. This allows ATC to track an aircraft's movements on their radar screen, so they don't get you confused with another aircraft. There are certain combinations of codes that mean different things:

7700 - General Emergency
7600 - Radio Failure
7500 - Hijacking

If you squawk any of those 3, you will start flashing on their radar screen and will have immediate authority over other craft. For 7500, (hijacking) you will be asked a simple question to which you answer 'Yes' or 'No' i.e. to confirm, your heading is 232 degrees? If you answer yes, you are confirming that there is a hijacking / terrorist threat on board. The idea is that the hijackers won't know the meaning of the subtleties of the question.

Hope that helps 😉

this also might be of interest

https://forum.flyawaysimulation.com/forum/topic/15950/squak/

so if u put that code in on fs u will get asked a question like that?

If I'm not mistaken, an aircraft squawking 1200 is operating under VFR, yes?

In any case, you set the squawk using the radio stack - the display is the one marked "Transponder".

Yes, 1200 is for VFR.

I also forgot to mention, FS9 isn't programmed for any of the emergency transponder frequencies.