What's the difference between "Walla" and "Chuffa?"

Screenwriters need to know the difference

What’s the difference between WALLA and CHUFFA, because they’re similar. WALLA is basically just background murmuring. Let’s say we do a scene at a baseball game. Two characters are sitting in the stands and we need to have background murmuring of the fan saying, “Ump, you suck!” “No batter!” “Hit a home run!” Stuff like that. It doesn’t go in the scrip…