Northern Crossroads is a MUD, or Multi-User Dungeon.

MUD2 is the successor of MUD1, Richard Bartle's pioneering Multi-User Dungeon.

The talker takes some cues from Multi-User Dungeons by being composed of rooms, for which users write the descriptions, and a visitor may wander through these using the cardinal directions.

This is most dramatically and entertainingly evident in her reports on the rising passion among computer users for going on the Internet and exploring Multi-User Domains, or MUD's.