PEOPLE. He linked this to GSF's terrain, so I'm assuming he's trying to sound smart and talk about the various lairs that dictate certain brick's building lair (aka if it's a standard brick, water brick, etc.) That is, if I remember the conversation correctly.
He still probably coulda just tried to discuss it in a more mature, fully researched thread and not assumed everyone knew what the fuzz they're talking about right off the bat.