Instant response

Hi, I am still quite new to this site. I have been playing some long games, taking days to finish. However, there were several times I experienced some instant responses from my components. I mean “instant”, their moves took place almost at the same time as mine. Is this kind of action pre-set? Someone have ideas how?

On the right side menu of correspondence games there is “Plan conditional moves” that is what you are seeing


i see. thanks!