The equilibrium here is when water is boiled in a closed circuit.
The point of equilibrium can be described to be the point where there are no opposing forces. At this point, there are no changes anymore.
In the closed circuit for boiling water, no air or water would be able to leave the pot while at the same time no air or water from outside would be able to enter the pot.
Read more on equilibrium here:
https://brainly.com/question/517289