A MUD is a online multi-user dungeon game. Historically MUDs have used a text interface, players would connect to the MUD game server using a telnet program. Some newer MUDs enhanced the text interface with a point and click client.
A mob is an individual or group of NPC’s that roam around the game. The term mob means mobile, it doesn’t mean mob as in an angry mob. Mobs tend to be monsters, bandits or other types of enemies, though it doesn’t have to be. In the current version of the Bedevere MUD Engine mobs are always an enemy.