When you're having a large-group "stream of conversation" in meatspace (in the lobby of convention hall, say), subgroups within the conversation will break off

When you're having a large-group "stream of conversation" in meatspace (in the lobby of convention hall, say), subgroups within the conversation will break off temporarily to form smaller "huddles" that step slightly away from the group, focusing on one-another rather than the group, to have a temporary "sidebar" conversation. Content from a "sidebar" conversation is usually taken far enough away from the larger group that it's not bothersome/interrupting the topic of the larger group; but—unlike a whispered aside—these temporary sidebar conversations are still public conversations, and they leak enough signal to the larger group that if someone in the larger group focused on the sidebar conversation, they could pick up the general topic of what's being discussed, and choose to join the sidebar discussion themselves. Hey, that's threads!