They would only have one waiting list, so the active waiting list would be it. And I would assume they place people on the wait list with some sort of ranking system...maybe not a complex one, but they may group people by a point system.
from what i understand most adcoms award points based on statistics (MCAT, GPA), personal statements/essays, and interviews. So they would total the points and rank people with that, then just start at the top of the pile.
By active, it means when a spot becomes available, such as the number of enrollees drops below their minimum after they have closed the application process, then they take that top piece of paper, copy the address, and send a letter of acceptance.
Good luck, I hope to see yall in tel aviv this fall!