what do you not understand?
edit: here's an explanation of what it does and why
when you first run the block with a true input, it will return true
however, when you run it again, it will return false
but once you run it with a false input, it will reset
and it will report true again with a true input
in the context of the right clicked hat, this is useful because otherwise it could erroneously detect being right clicked when the user mouses over the sprite while the right mouse is down.