• how does path work in the code?

Question related to mission The Flat Dictionary

I solved the problem and i have a general idea of how the code is supposed to work, but this line of code is really stumping me.

path, current = stack.pop() how does it assign path and current when theres only 1 stack.pop() on the right side of the equation? if im not mistaken path is supposed to be the string of key/key's you've been accumulating, how does that work?