Borusyak, 2021 has a sentence
We further discuss the implications of our results when treatment is simultaneous rather than staggered, when it can switch on and off, and when multiple treatment events can happen in the same unit
There are three treatment styles in the above sentence. From my understanding "when it can switch on and off" means that the laws can be implemented and remove after a period in the same country. But I am reluctant for the definition of the other two treatment styles: treatment is simultaneous and multiple treatment events can happen in the same unit.

From my understanding," treatment is simultaneous" is that all countries passed a law at the same time, is this correct? And what is multiple treatment events can happen in the same unit ?